About 5 minutes per washer on the lathe. Start with a 1/8" thick fender washer with a 1 1/2" OD and machine a step 1/16" deep, or just modify the existing lower spring washers. Experienced race engine builders have done similar stuff many times. Any wrench jockey can assemble OEM parts. Small block V8 springs offer a lot more selection where seat loading, lift capacity, and max RPM is concerned.
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!