If you can find valves with the same stem diameter that are slightly oversized in head diameter and/or stem length, any good machinist can cut them down to fit. Just don't use an intake valve in an exhaust port- - - -the alloy probably won't handle the heat load for very long. I believe the intakes for those engines used 30 degree seats, but a 45 degree valve can be reground to 30 without much of a problem.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!