You are looking at a NOS GM Chevy LS6 454 high dome piston and pin, pt# 3976026. That number comes up as .030 over bore according the GM parts books. The piston diameter is 4.250. It is stamped with 3976044 which I believe to a superseding number. Correct for 1970 LS6 450 HP or the over the counter LS7. Recently found in the attic of a 70’s drag racer. It’s a little dusty but still NOS GM.