318 crank into 340? pitfalls

thanks for the info on pin size ck,nm9stheham.thats something I hadn't thought of.with everthing that had been done to this thing you could be right.I have a full set of 307 chevy rods that I took out of my nova when I put in a GM create.Is that something that gets done a lot?any probs getting pistons to correct bore and wrist pin size?