water pump for 360 mild race

I ran into an issue running the 8 arm impeller with a stock 68 A/C pump pulley. I was getting cavitation pits on the front cover. I shift at 6400 and cross the stripe at 6700. I bought a new 8 arm pump and went in and cut off 4 arms (chasing hp) and put an anticavitation plate on it. Problem solved. Still bumps off the thermostat at idle. On the highway it will go up to 205, but that is more the 4:10 rear gear.