Without reading this whole thread:
1. Check water pump - the divider plate spacing could help
2. Check fan clutch - (I wish I had, that was probably my own biggest contributor to heat issues).
3. Add cooling - Aluminum radiator is pricey but can help
4. Check baffles
5. Check thermostat - leave it in - taking it completely out will not allow the coolant to cool-off while in the radiator.
6. Check timing - bad timing can add heat
7. Add an overflow catch tank if you don't have one. A big helper in radiator life span as well.
8. Make sure you have a fan shroud and that the fan is inside the shroud the correct amount.
My two cents,
Scott
#5 is theoretically possible on some engines but Pontiacs have enough constrictions built in that we are looking for more flow, not less. I know this because I've tried it with and without a thermostat on a few engines. They either cool better or stay the same without a thermostat. On a Pontiac v-8 the thermostat is only useful to quicken the heating up of the engine.
