Did the factory use different pulley sizes for slant with AC?

Ditto on the tight fit to the radiator. That is why they recessed the water pump housing into the side of the block, which also saved money (no separate w.p. housing). I don't think you can find a clutch fan which will fit an A-body slant.

My 1969 Dart had factory air and power steering. It had 3 V grooves on the crankshaft pulleys. I recall the water pump & alt used just 1 belt, AC belt (wider) was alone (innermost on crank) w/ an idler pulley, and p.s. was a separate belt (outer-most) w/ no idler. I think 1970's Darts changed to 2 belts on AC, alt, & w.p., but Google Images would answer. Some later cars might have had 4 V grooves at the crank, almost certainly after they added those !#@! smog air pumps by the 1980's.

I think all AC cars bolted a pulley on the inside of the damper. That special pulley has a big hole to fit over the snout of the timing cover and you must remove the damper-pulley to install it. It fits up very close to the timing cover, almost scuffing the paint. I know since I had to buy one for my 1964 Valiant slant to add AC (Sanden compressor on custom bracket). When pulling the damper, never pull on the outside, and only from the bolt circle inside the rubber strip. Good luck.