Try and hire a lawyer who specializes in collectible vehicles??

Another option is to let insurance company total the car, take the money (after putting up a fight and getting the amount increased) then (assuming they let you) buy the van "for parts".

Usually you can buy the totaled carcass from the insurance company for a few hundred dollars.  Get it fixed yourself by a good bodyshop (hopefully cheaper than the first estimate).

You then have your van again and some cash.

Only downfall is vehicle will most likely have a salvage title and require an inspection or two before you can put it on the road....but better than it being crushed.