Help me diagnose why my head gasket blew

The pistons come out of the hole already with this block. And the heads are going to get resurfaced so that will lower the combustion chamber volume increasing compression even more. So to make this block work I would need to get a thick MLS head gasket. So the shop and I agree that I would be better off starting with a fresh block.

No this is a different machine shop. I built the engine originally while I was down in AZ. Now I am in PA. This shop was recommended by a friend who races every weekend, and I trust him.