Probably 7-8 years ago, when I went to buy new belts for my 79 403, they sold me the wrong ones. Turns out the listing in their books was wrong, and I think it was listing 400 belts for the 403. That might have happened to you too, so could be why you have belts that don't fit. Anyway, I found the right belt sizes and these are them:
Power steering pump and the alternator both use the same length belt, which is 15470.
The original a/c compressor belt is 15595, but don't know if it will work with your new compressor.