I think that running without a thermostat or with a restrictor only are both poor ideas for any car that is anything more than a dedicated trailer only race car.
Just because racers do something it does not mean it is a good thing, especially when you do not know why they do it.
Why do racers run without a thermostat or with just a restrictor?
It sure ain't because they are overheating with a thermostat, they don't run long enough.
It's because the restriction of the thermostat, coupled with high rpm's were blowing hoses and such loose. It's a crutch to fix a unique issue.
Much like the old wives tale about needing a thermostat so the coolant has time to get the heat out of the block is false. Whomever says this doesn't know about heat transfer. The number one factor, by far, in heat transfer is the differential between the high and low temps involved. Not the time in contact.
The bigger the difference in temp between the block/heads and the coolant the quicker the heat transfers. This is something that is not commonly thought about, the same it true about the difference in temperature between the coolant and the AIR going thru the radiator.
Turbulence in the coolant can increase the efficiency of the heat transfer. Best way to create turbulence in our applications is to increase flow, but not to increase it so much that the pump cavitates. If you were to compare an intercooler to a radiator (both designed to remove heat from a "fluid") you will see that intercoolers use internal devices to create turbulence thru the intercooler, this increases efficiency. Radiators don't generally do that because you can increase flow without detriment unlike in an intercooler where too much flow (boost) can cause all sorts of interesting things to happen.
As to the OP's specific situation, a 10 degree drop by swapping the pulleys is fairly large. You are probably ok now. If you need a bit more I would suggest a high flow pump with an anticavitation impeller, or at least putting an anti-cavitation plate on your stock pump.
