Scott, you've always been a pro in every correspondence and transaction. Though I have no 'real' low speed cooling issues on my 74 (FlowKooler also), it flirts with 210 w/AC on at idle sometimes. That's it, hasn't overheated in 5 years since.
Yet I'll measure my pulley vs. yours.
If only a bit smaller, will still install to give any results I can share, for low and high speed. If the same, I may do it anyway for the bling factor!
I concur with George and his research that the greater volume of FlowKooler basically eliminated my problem. (Also purchased on his recommendation.)
Since I don't drive my car at 145mph very much (!) I'm just going with the fact that more water flow can only be a good thing.
Again, thanks for your work, effort, and attitude in this rather minuscule market.