Even with a good compression test, it still could be a head gasket. You are doing everything I'd do with a pressure test on the cooling system and a cylinder leak down might be a good idea as well.

The fact that sometimes you aren't getting circulation to the radiator suggests either air (not vented or head gasket) or maybe a water pump issue. Might be worth replacing the radiator expansion tank cap as well (cheap and they do fail).

I've always heard that not running a thermostat will overheat these cars but have no personal experience.

I am using the stock radiator; it ran perfectly cool the first few times I had the car out. The over heating is intermittent, so I’m not sure about the radiator since I know there is air in the system. My buddies and I are in the process of installing the suspension now (getting the torsion bars in was a special level of hell) so I may not get to the cooling system pressure test until this weekend or next. I will be installing a new thermostat. I definitely will be doing a leak down test after if I don’t get any results from the cooling system pressure test. I’ll post the results.

Alright guys, I hooked up the radiator pressure tester this weekend and right off the bat, water started spewing from one of the reservoir hoses. I tightened it up and ran the car, the radiator was still intermittently going hot cold hot cold. We put 3 sets of eyes on the engine and finally we tried to spin the pump.... and we could. The belt was too loose. Tightened it up and let it idle for 15 mins, no more over heating.

Finally having that resolved; what size oil coolers are you guys running (HxL)? I've been thinking about getting something like 13"x6" or 11"x8". Also, off topic again but what brand shift lights have you used? I've tried two but got neither to work (using the tach signal and trying the coil signal too).