I've used small block Chevy V8 valve springs, spring retainers, and split keepers on stovebolt engines with no problems- - - - -frequently. They're cheap and plentiful. Even the V8 exhaust valves will interchange with no problems and they're available in stainless steel.
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!