The easy answer is that as long as the van is 25+ years old you're good to go, but the reality is the much of this depends on where and who you use to get registration.
WA department of Revenue is where I faced my biggest challenge. Both the EPA and NHTSB regards are clear about what is needed for import. However, the DOL couldn't look up a True Value based on the VIN. The VIN is only 13 characters long and they were looking for a 17 character VIN and couldn't or wouldn't use fair market value or the amount I paid for the paperwork. Ultimate I got an estimate of valuation from an Auto appraiser and found that I needed to time my registration for when one of two clerks was in the office. The other simple wouldn't do the work, refusing to help because the VIN was an unexpected length.
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