Use stock 1970 340 rods in rebuild?

Maybe, just maybe..... you might want to just go with a new set of rods......stock 340 pistons weigh a ton....couple that with any serious rpm and there is a recipe for a spun rod bearing. NOT saying you will, just something to think about on your own......I'm not gonna tell you how to spend your money.......originally I was gonna say just have the big ends checked, if they are in spec, use them as is......the power level you are speculating is not that much of a stressor.

Good luck!!