It's possible for a good machinist to alter either/or both the stem length and head diameter on a valve that's close to the dimensions of an original equipment item. If the stem is shortened and new keeper grooves are machined, use a hardened steel lash cap to prevent wear to the top of the stem.
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!