Project "Chihuahua" '65 Formula S Restoration "Estilo Mexicano"
The crank pulley is between 6" and 6.25". Doing the math with the water pump pulley @ 5.75" it seems the water pump is slightly overdriven 1.04/1.08.
I saw a table in a factory manual somewhere, showing that engines for the a/c equipped cars did indeed have a water pump pulley which was slightly smaller than the crank pulley. So yes, A/C cars did have an overdriven water pump according to that table.
I believe that table was for the 273 Commando engine, but it has been a few months since I looked at it. If I find it, I'll post a link here.
Source: I was curious why, when I was a kid, our 273 Commando, A/C-equipped 1967 Barracuda tended to overheat. I had been told the car came without A/C and A/C was added later. The pulley size should reveal it that was true, thus this caught my attention (that the water pump pulley should be smaller).
Now the car has a 318 engine in it (I have the 273 stored), so I was pondering what size the water pump pulley should be for the 318.
I must go measure the pulley sizes on that 273 to resolve the mystery. Also, my restorer says there was no such option, no "a/c-ready" car, as the firewall is slightly different between a/c and non-a/c cars.