Go electric
If you'd consider this....I just happened to replace my belt driven fan (non-clutch, it was always spinning) with an electric fan i bought for $60 from O'reiley auto parts (my local auto parts chain.) It was an S-type, low profile stock replacement fan that i just wired up, and installed a switch on my dash. The fan zip-ties directly to the radiator and is built in to its shroud, so you can remove your stock shroud, and have allot more room in your engine bay, especially if you mount it in front of your radiator. I switched to an electric fan mainly to free up horse-power, but it also draws ALLOT more air through the radiator since it is mounted right up against the radiator. My '65 is just my toy, so i don't mind paying attention to my engine temp gauge and flipping on the switch when i see the temp rising, or while sitting at a long intersection. You can also get a temp actuated switch(which is a bit more pricey) and the fan will kick on and off at pre-set temps, and there is still no direct draw on your engine. I actually hardly have to turn on my fan, and it gets well over 100 degrees out here lately, and when i do turn it on, my temp drops well below 190, which is below normal operating temp and my electric choke sometime doesn't turn off. Anyway, food for thought...