I bought theses pistons a while back thinking they were OEM 11.5 - 1. but now I'm not so sure of the origin. They are standard size have a small .065 dome, .085 valve reliefs and TP in a triangle on the under side of the piston. A comp height of 2.055. These old slugs are in pristine condition. I'd like to bore a 413 truck block .070 and race em. If the part # would be helpful I could run to the shop and check.