Need help ID'ing Pistons

[Tmwoodall]

I am trying to figure out if the PO was shooting me straight, or if I should just start totally over on this engine. These are supposedly TRW pistons. THe only markings I can find say U.S.A, and on the I believe 42 31P on the inner wall where it mounts to the arm. Nothing besides the .030 stamping on the top. I had this running years ago on the stand but decided to put a better breathing Edelbrock top end on it. So I'd really prefer to not pull them out, hence the cramped photographing area.

Any help? I was hoping to find a casting number so I could easily determine my compression ratio. Any and all help would be greatly appreciated.