340 Piston identification. Silvolite?

nick455440 said
Hit “post”prematurely, performer rpm intake and was looking at some of the lunati cam and lifter kits,

Put 11/32 stem valves in those J heads, like a +.100 1.94 /1.60 for a chevy. You can get a set for under 100.00 bucks
Cuz if you're going to do guides anyways may as well put a lighter valve in there.