[JP Noonan]

You can remove the induction system, then the dizzy, then the rear tinware, then the two side tin pieces. The driver side tends to get hung up on the dipstick. I've done this several times to replace a broken cht sensor, and to clean the cylinder and oil cooler. Takes a few hours but not difficult. You can then get to the top head nuts.

Compression should be at about 110 for an older motor, 135-150 on a new one. I'd make sure that the lifters aren't hydralic. Do a leakdown test, remove the head gaskets. and make sure a ring hasn't broken (I think you mentioned before that you weren't sure if you put the rings in correctly)

Before all that maybe try a leakdown test, it will tell you weather it is the rings (air coming out the oil filler) the exhaust valves (air coming out the exhaust) the intakes (air blowing out the carbs, or the head gaskets. Or if the leakdown percentage is low I'd say your deck height is too high or you used bus pistons.