In my experience(and I've built 4 of these SOLID from the ground up), but I'd say rebuild your setup.. don't half-ass it..

These engines are bullet-proof, but your sounds like it needs a good freshing up. A new Marnel/AMC head is $350. Then any machine shop you like can do anything else..

These engines have indestructuble bottom ends. And they are cheap to rebuild.

A new 2.6 can be redone for under $1000. Simple as that. I'd say do it !!

Jason