Jeremy, I have a similar combo to yours, with RPM heads and 10.5 to 1 compression, and I run mid-11's. Mine is 99% street driven.
I've had similar problems to the ones you describe, and just when I thought I've found the answer, the temp gauge begins to rise again! I've read dozens of articles on Pontiac cooling, and there is no one cure.
I can tell you what I've tried, what has worked, and what has not worked.
I run all the factory "400" baffles and dams (it's a factory 400 car, so nothing I had to do there).
I run a 180 thermostat, with a small hole drilled in the outer disc to alleviate excessive suction on start up (the famous collapsed upper hose problem).
A FlowKooler pump is a waste of money. The problem with our old Pontiacs is NOT the volume of fluid we're circulating. I learned that lesson about 5 years ago, and many fellow Pontiac racers have confirmed this. My wallet was $80 lighter, same problem. I went back to the factory steel water pump. Just make sure you have the correct divider steel plates behind the water pump.
I run a 2 row aluminum radiator (Summit Direct Fit version) painted black. I've tried electric fans only, and it's never worked. I've tried one of those massive Hayden stainless wide-blade flex fans (btw, those blades are VERY sharp), and while they pump a heck of a lot of air, the factory clutch fan worked the best.
I also run the factory fan shroud, which is still available from GM, or as a repro through a resto house like Ames. You're fan should be spaced so it's half in/half out of the shroud. I also run the factory w/p and p/s pullies.
I used to have an electric fan as a pusher, mounted in front of the radiator, and it was thermostatically controlled to come on at 190 degrees. This helped, but again, with a desire to stay with a stock look, I decided to pull it. The electic would come on a super hot days when stuck in traffic, and the temp would come back down to 190 from around 195.
I now run an 18" black thermostatically controlled clutch fan, available through Summit Racing. Looks stock, and pumps a heck of a lot of air. I had to shelve my factory 19-1/4" unit because I occasionally had some interference with the factory fan shroud.
One of the biggest changes I performed to cool the car down is that I went to full manifold vacuum instead of ported. I modified my vacuum advance can to pull full open at 5" of vaccum, so I get 36 degrees of timing even at idle (some racers have a locked out advance, and run 36 all the time). At cruise, I can pull 40-45 degrees of timing.
I also run Water Wetter and straight water, and I have a an overflow/recovery system with a 13 lb cap. The recovery system also helped quite a bit, as it adds a little bit more capacity to the system.
To recap my setup:
- 180 thermostat, with bypass hole - straight water, with Water Wetter - all baffles and dams in place - 18" thermo clutch fan - factory shroud, with fan located half in/out of the shroud - full manifold vacuum - 2-row Direct Fit aluminum radiator - overflow/recovery system - 13 lb cap - stock pullies
