13:1 Compression Pistons in 340 Small Block

I have no problems with those pistons
as YR said
not at 13:1
Will NOT work with aftermarket closed chamber heads without even more work
and I'd check with clearance with more modern than X-J combustion chambers
They are heavy so not for a high rpm build today
(back then High RPM is not what it is today)
as said theheads limit power so no reason to shoot for high compression
As YR says you have to build for some quench on the back side of the chamber (OUT OF THE DECK) and cut/ mill the domes for whatever compression you want