72 340 short block

today i picked up a 72 340 short block for 50 bucks.the bearings appear to be in good shape,and it has no ridge.but the bores have surface rust and the piston are 40 over stamped with L2316 .040.does any body know if these are cast or forged,and what the comp ratio is?also what is the over bore limit for this year 340?is it possible to clean the block and re-hone it and re use the pistons?thanks -wade