I think that's a Chevy piston. I've seen SBC pistons used in early 318s w/full floating pins and the valve spacing is off on them. See the two below if they come out... First is a SBC 327, second is SBM 318. There are differences but I've seen them run once you overcome them.
Edit - after looking closer... Nope. It is a 318 piston...
What cam do you have in it?
