I agree, you should inspect the cylinders for scoring. When I pulled the head off my old setup (similar to yours), one piston had been replaced and there was deep scoring in 5 & 6. You never know. The PO told me it kept blowing head gaskets. Apparently he was having some severe detonation problems. An old inefficient turbo, lack of intercooler, high compression pistons and jerry rigged fuel system is a recipe for disaster if you're not careful. I considered water injection before I just ditched the whole thing after I found out the bottom end was trashed.