I'm using a stock repro crank pulley. My water pump pulley is some after market aluminum that was about a 1" maybe smaller compared to a stock style non-AC water pump pulley.
Could you please post a pic of your setup?
I have a two-groove crank pulley with the larger front power-steering pulley (not used), and a single-groove water pump pulley driven from the smaller inner groove on the crank.
The rims on both are almost touching, and if the upper got very much smaller it wouldn't clear the pump housing bolts.
In the spring I'll see what a high flow 160 thermostat will do
Not much, just make your engine warm up slower. The stat only sets the
minimum temp - the max is limited by your cooling capacity vs. the ambient temp.