Thanks for all the info- - - - -I think I'm going to go with an .090" mill on the 261 heads, and be satisfied with that modification. I'll recess the intake valves to put the protective shrouding back in, and probably increase the exhaust valve size to 1.6", using the hotrod small block V8 stainless valves. The bored and stroked 261 engines I've got on the drawing board will also have close to 300 cubic inches with Japanese diesel pistons, H beam connecting rods, and slip-fit flanged removable sleeves.
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!