1965 vs 1966 273 AC accessory drive

I agree. Google Images more. The 1965 doesn't have the correct stamped metal alternator bracket. I recall 1970 was the first year the small block had the 2 inner belts for AC. Are you sure dealer-installed AC was the same as factory AC? I know the firewall varied between AC and non-AC cars in 1965, so there definitely was factory AC. My 1965 had a "Western Auto or Sears" installed AC, with a monster Tecumseh cast-iron compressor, same form-factor as a York but as heavy as an RV2. Not putting that beast back on. The brackets were about as clumsy as in the schematic above. AC was still a rare and expensive option in 1965.