340 PISTONS: Between a rock and a hard place

Your standard bore block is already prepped? are the bores straight ? no taper?

It's possible. My Ford 400 block cleaned up good with .0002" taper on the worst cylinder.

Forged pistons require more clearance.....especially the older ones. They swell up pretty good when they get hot. He might have good bores. Mine turned out fine.