Overdriven pulley how much is too much?

My combo is under-driven in the hopes that the V-belt will stay on the pulleys at 7200. In 20 years, so far so good.
I fixed my overheat issues decades ago by running my pistons and top gap a hair loose, and with a 7-blade all-steel fan off a mid-70's A/C equipped 318 Swinger. Same car donated it's rad. I run a thermostatic clutch, and the coolant runs 205 .And yes, to the obligatory hi-flo pump.