When you had the heads off, did you carefully inspect the heads of each pistol to insure there were no cracks or holes in the top of any piston?

Even a small hole is a pistol will kill its operation, It will not have vacuum to suck in the gas/air mixture during the intake stroke, it will not hold pressure during the power stroke, and it will not have much compression during the compression and exhaust strokes.

1977 CJ-7, fiberglass body, AMC 360 w/ headers, DUI ignition, Edelbrock intake and Holley 4150 carb, TF999, Dana 300, 4.56 gears lockers, York air comp, 4" susp lift, 2" body lift, BFG 35" M-T tires, Megashifter, AGR pump & box, REP8000 winch.