I live in CA and have a SBC in a '53 Studebaker. Everything 30 years old and older is smog test exempt. But don't count on that forever. There is legislation in progress right now to lock the smog exempt date to 1976 (I think). No more sliding scale. SEMA is fighting it along with many other automotive hobby organizations.

Go ahead and do what you want with your '46. I don't think you will have a problem. Double check with DMV just to be sure.

Pat