I would think a car built for export may not meet Fed/Calif emission requirements and therefore not legal to register.
Nope. All export American cars were legal to register in the U.S. All of them all had all of the safety stuff back then, glass, lights, frame and crash reinforcements. I know Mercedes, BMW, Jags, and other vehicles had to be converted to U.S. safety specs before they were allowed to be shipped (imported) to the States. Eventually all cars (except 3rd world junk like Russian and North Korean garbage) were built with the worldwide safety criteria.