Ailing engine (Updated after teardown)

Jack, as suggested earlier either the block or the heads need to be o ringed. Under normal street driving with the blower you won't normally have a problem. But when you get into it, the boost is trying to push the head gaskets out. That is ONE of the shortcomings of the SBM with only 10 head bolts per side. I had the same problem, albeit naturally aspirated with 13-1 compression in a 273 back in the early 70's. Ed Hamburger suggested I o ring the block or the heads and run his copper head gaskets. After I had the heads o ringed and used the coper gaskets, I didn't blow out any more head gaskets. Just my .02!