Diagnosis of issues -
Engine was not a low-mileage take-out. It had been rebuilt and was .040 over. Additionally I found stampings on the back of the deck that indicated that .007 had been taken off the decks. That would have been fine had they used the 010 thicker head gaskets, but they used stock thickness which resulted in the piston/valve contact. Valve guides in the heads were shot, as were the seals which is where a lot of my oil consumption had been. Ring end gaps were huge, and cylinder/piston clearance was 008-010. I don't know how this thing went 60K miles.
New stuff.
Military surplus Navistar block. Navistar started casting the blocks around 2000-ish when GM moved away from the 6.5. They increased deck thickness as well as web thickness and changed the formulation in the metal. New block weighs about 60lbs more than the old block.
Bought a torque plate.
18:1 compression pistons with ceramic tops and microslick on the skirts.
Everything was dropped at machine shop last week. More pictures as things progress.