[alabama mike]

I can't answer for California, but here in Alabama the vin follows the cab, so putting a 77 cab on a 74 the truck would be registered as a 77. Or as long as you keep clear records and receipts you can have the state issue you a new VIN (saying you want to change vehicle designation from a 2 ton to a 1 ton). Best thing to do is find the California code and start reading, of find a shop in the state that has done something like that in the past and see the steps they've used.