According to the "wrangler" and others I've talked to, California used the engine # for the VIN in 1952. I know they did this in 1946, as my 46 is registered with it's engine # as the VIN.
The purpose of the new ID plate is to make a connection between the engine (VIN) # and the truck since it won't have its original engine anymore. Since this is the case, EVERY 1950's Chevy/GMC truck in California that has had an engine swap is in the same boat. There are thousands of them.
It's not our fault that California chose to use a replaceable item (engine)to tie the VIN to.