For some reason I can not get a reply to go through, so I have to send a new message. To my best knowledge ( and I sure don't know it all ! ) I can't bore a 413 to a 440 piston. I can go to 426, but cylinder walls would be thinner than I would be comfortable with. I haven't measured bore yet, but there is no oversize stamp on top of my pistons. Engine reported to have only 68,000 miles.. And they are dished pistons which are very low compression Can someone tell me if the Mopar factory used cast or forged pistons on new magnum 383 and 440? What is your opinion on cast pistons below 10:1 comp. And 6000 RPM ? Thanks for your input......................MO........SW IOWA ---- Please address private mail -- mail of interest to only one person -- directly to that person. I.e., send parts/car transactions and negotiations as well as other personal messages only to the intended recipient, not to the Clubhouse public address. This practice will protect your privacy, reduce the total volume of mail and fine tune the content signal to Mopar topic. Thanks! '62 to '65 Mopar Clubhouse Discussion Guidelines: http://www.1962to1965mopar.ornocar.org/mletiq.html.