State guides

All 50 states have a page. Every fact on a state page cites an official source (state agency page, statute or rule, or the federal HS-7 form) and every page lists what was not verified. The groupings below use only what those sources say; a state in a middle group is not "average", it is a state whose sources were silent on the 25-year question. Read each page's gaps list before relying on it.

Kei and mini-truck titling, where an official source speaks to it

Official source describes a kei / mini-truck title or registration path

Arkansas: Ark. Code §27-14-726 defines 'mini-truck' and lets it be registered as a Class Eight farm vehicle; not allowed on interstates, controlled-access highways or roads posted above 55 mph.
Indiana: Indiana BMV has a mini-truck title checklist (first-time titles issued by the BMV Central Office); whether a given kei meets Indiana's mini-truck definition was not verified.
Michigan: Michigan: kei-class vehicles (including mini-trucks and microvans) 25 years old and older can be titled and registered for on-road use; import documents required.
Nebraska: Nebraska DMV has a Minitruck title category (statutory definition: engine ≤1,500 cc, ≤67 in. wide, ≤4,200 lb dry weight, hauling bed, enclosed cab, listed equipment); title at the County Treasurer within 30 days of purchase.
Oklahoma: 47 O.S. §1151.3: mini-trucks are titled and registered like other vehicles and may use roadways except Interstate highways; §1105(F) says the bond-release-letter rule does not bar titling mini-trucks. Whether a given kei meets the mini-truck definition (OAC 260:135-7-126) was not read.
Tennessee: The county clerk guide says mini trucks can get a medium-speed registration (top speed over 30 and up to 35 mph, 49 CFR 571.500) or a Class I plate; it does not say how a faster or imported kei is treated.

Official source allows it only with stated limits

Kentucky: KRS 186.077 allows a minitruck to be registered as a 'street-legal special purpose vehicle' with a motorcycle plate, only where a local ordinance allows it, never on interstates/parkways or federal-program highways, and no more than 20 miles on centerline-marked roads.
New York: NY DMV will not register or title a Kei-class vehicle unless the applicant proves it was brought into compliance with the applicable FMVSS and EPA requirements.
Wisconsin: A kei without an FCL or RI label gets a 'NON USA STANDARD' title brand and may only be registered with collector (special interest) plates; the page cites Wis. Stat. 341.10(6) for model year 1970 and newer.

Official source says kei vehicles cannot be titled or registered

Georgia: Policy Bulletin MVD-2023-05: Georgia prohibits titling and registering Japanese kei vehicles and minitrucks, even if titled in another state.

No kei or mini-truck rule found in the sources read

Alabama, Alaska, Arizona, California, Colorado, Connecticut, Delaware, Florida, Hawaii, Idaho, Illinois, Iowa, Kansas, Louisiana, Maine, Maryland, Massachusetts, Minnesota, Mississippi, Missouri, Montana, Nevada, New Hampshire, New Jersey, New Mexico, North Carolina, North Dakota, Ohio, Oregon, Pennsylvania, Rhode Island, South Carolina, South Dakota, Texas, Utah, Vermont, Virginia, Washington, West Virginia, Wyoming. This does not mean kei vehicles are allowed or banned there; it means the pages read were silent.

Overall: how the official sources treat 25-year-old imports

Official text expressly permits 25-year-old imports (6)

Alabama: Rule text expressly says vehicles 25 model years and older can be titled and registered with proper ownership documents.
Alaska: State DMV page expressly says legally imported vehicles 25 or more years old can be titled and registered without current FMVSS compliance.
Idaho: Idaho Transportation Department policy says a gray-market vehicle at least 25 years old at import can be titled without a DOT bond release letter, with a brand.
Michigan: Michigan says kei-class vehicles 25+ years old can be titled and registered for on-road use.
North Carolina: Title Manual says vehicles 25 years and older need no EPA/DOT release letters.
Virginia: Code of Virginia §46.2-602 exempts foreign-market vehicles made 25+ years ago from the federal-compliance proof.

Titleable, but branded or limited to restricted plates (2)

Missouri: Imports without a U.S.-standard MSO are branded Non-USA Standard; HS-7 Box 1 (25+ years) is not on Missouri's list of ineligible boxes.
Wisconsin: Vehicles without a U.S. certification or registered-importer label can be titled but are branded and limited to collector plates.

Process documented; 25-year treatment not stated in the sources read (26)

Colorado: Documents are listed; the sources read do not say how a 25-year-old exempt vehicle is handled.
Connecticut: The DMV page describes a grey-market conversion process and does not address the 25-year exemption.
Delaware: Rule is stated only for vehicles under 25 years old; treatment of 25+ vehicles is not spelled out.
Florida: Documents listed; 25-year treatment not stated.
Illinois: Rule text dates from 1986; 25-year treatment not stated.
Maine: Maine's BMV pages describe a VIN inspection for imports and an age-based title requirement, but no customs or compliance list was found.
Maryland: The MVA page lists HS-7 Box 1 as acceptable but also says overseas vehicles must meet FMVSS, EPA and Maryland standards.
Massachusetts: Documents listed; 25-year treatment not stated.
Minnesota: DVS lists three federal forms and says more proof may be required; the 25-year exemption is not addressed.
Mississippi: The FAQ lists import documents; the 25-year exemption is not addressed.
Montana: The title manual requires bond release letters for non-complying vehicles and does not address HS-7 Box 1 (25+ years) vehicles.
Nebraska: Import page requires DOT and EPA stickers or equivalent documents and does not address the 25-year exemption.
Nevada: Industry guide brands foreign/gray-market titles 'Non-US Vehicle' and does not address the 25-year exemption; it says such vehicles must be brought into compliance, exported or destroyed.
New Hampshire: Rule lists import documents including HS-7; the age rules for titles were not verified from an official NH page.
North Dakota: Manual lists documents for imported vehicles; the 25-year exemption is not addressed.
Ohio: Documents listed; 25-year treatment not stated.
Oregon: Oregon accepts a CBP 7501, manufacturer letter or label check as proof of U.S. standards; how a 25-year exempt vehicle satisfies it was not found.
Pennsylvania: Rule is stated for vehicles made not more than 25 model years ago; EPA 3520-1 is not required for vehicles over 25 years old.
Rhode Island: RI DMV lists CBP 7501, NICB and VIN inspections; the 25-year exemption is not addressed.
South Dakota: Dealer manual lists CBP 7501, HS-7 and EPA 3520 papers; the 25-year exemption is not addressed.
Tennessee: Tennessee asks for a photo of the vehicle's FMVSS label; the sources read do not say what is accepted for a 25-year-old exempt vehicle, which has none.
Texas: Rule is stated for vehicles under 25 years old; 25+ treatment is not spelled out.
Vermont: VT DMV requires import paperwork certifying U.S. emission compliance; the 25-year exemption is not addressed.
Washington: Customs paperwork listed; 25-year treatment not stated.
West Virginia: Statute lists ownership documents with notarized translations and, for some countries, proof of Clean Air Act and Motor Vehicle Safety Act compliance.
Wyoming: The WYDOT page lists federal documents under a heading about vehicles under 25 years of service; 25+ vehicles are not addressed.

Official sources state barriers or hold-ups for typical 25-year imports (8)

California: CARB says the Direct Import program has no exemption beyond model year 1967 and older; treated as very hard.
Georgia: Georgia DOR policy bulletin says kei vehicles and HS-7 Box 1 (25+ year) imports cannot be titled or registered.
Kentucky: Statute for vehicles not made for U.S. sale requires DOT and EPA bond release letters and contains no age exemption in its text.
Louisiana: OMV policy says grey-market vehicles must be converted to comply with U.S. standards and does not mention an age exemption.
New Mexico: MVD manual says not to process imported-vehicle transactions without a CBP Vehicle Release showing DOT, EPA and customs compliance and the waiting period.
New York: DMV can require state safety/emissions compliance even when federally exempt, and will not title kei-class vehicles without proof of FMVSS/EPA compliance.
Oklahoma: Title statute for vehicles not made for U.S. sale requires EPA/DOT bond release letters and has no age exemption in its text; mini-trucks are carved out.
South Carolina: Statute lets SCDMV brand vehicles from abroad that do not meet FMVSS 'Off Road Use Only', which blocks registration.

Not enough official information retrieved (6)

Arkansas: Only the mini-truck statute was read; Arkansas's general import titling rules were not found on an official page.
Hawaii: Only the registration statute was read; county import pages were blocked.
Indiana: Only mini-truck and out-of-state checklists were found; no import-specific official page was read.
Iowa: Only a statute using the term 'foreign vehicle' was read; its reach to overseas imports was not confirmed.
Kansas: Only a regulation on 'used, foreign vehicles' was read, and its reach to overseas imports was not confirmed.
Utah: The Utah DMV page read has no import content, and the import statute could not be retrieved.

Groups are ordered from most to least favorable on the question asked, but "documented, 25-year rule not stated" is not a ranking of difficulty. Within each group states are alphabetical.