I sent a 1963 Cooper 'S' Mk.1 to California and there was no problem. However, it is a genuine 1963, as restored by me for historic motor-sport and my best friend was the guy who imported it and he still has it. There were no issues and it was very easy. He had driven it in competition in Europe and even had the documentation to prove he had owned it for over 12 months in England, so no duty was payable.
The value of a Mini in the USA is no higher than here and most car thieves/car 'ringers' who are just doing it for profit will not bother as the profits will be small in relative terms against the risks. More money can be made shipping harder-to-identify antiques to the USA or elsewhere.
When a Mini is stolen, it will make more money with less risk if it is stripped and the parts sold over a period of time. A good body-shell will always fetch good money here, as will all the other parts.
Not every Mini sent tot he USA is a stolen car, most are either genuine cars which meet the regulations, or are 'age-altered by owners returning to the USA after being based in the UK or Europe and getting into Mini ownership. This 25-year rule and making later cars appear to comply has, IMHO, very little to do with car theft and more to do with stupidity.
Edited by Cooperman, 20 December 2014 - 01:01 PM.