Use regular cast iron seat rings. RUN- - - -do not walk away from stellite hard seats! If you can find stainless steel exhaust valves with the correct length, stem, and head diameter, use them instead of buying into the myth that the exhaust needs hard seats.
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!