I.D. 340 parts

I'm also wondering if the bores and pistons are oversize.I found a "40" stamped into each piston top so I think they might be .040" oversize which means the block has been overbored already.There's also what looks like a date casting on the inside of them which is a "76" on the top line and "428P" below that.Anybody know if these are aftermarket pistons? Maybe from 1976?

The cylinders have a real slight ridge and some light scratching so I'm hoping I could get away with just re-ringing it but ideally it should probably get bored out with new pistons.Can you go .060" over on 340 blocks? I'm not planning an all out race motor,just a stock style redo.