Some years like 70, 75, and 78 tended not to have smog pumps so there was a different crank pulley that had the front groove spaced out to align with the alternator and a single groove water pump pulley to match. You want to get that stuff as a set and also include the timing indicator because those varied slightly over the years too. Another change was in 75ish they went from the dual groove AC PS to a wider single groove, this was to give more clearance with the larger diameter HEI distributor. If you are not running AC its no big deal to just run a shorter belt straight to the PS. IF you don't have PS its even easier. AC and no PS you will have to come up with a way to tension the AC.
500cid.com sometimes has used pulleys and also has new pulleys. I think they even have a billet aluminum set if you have that in you budget. They also have the plugs to plug the holes in the head along with just about anything else you could want for a 472/500/425.
Some people have reported being able to modify the alternator mounting to shift it further back. Seems to me it was already pretty close back there. I can't remember if this was using the stock physical size or maybe a newer more compact design. Other guys have shimmed the PS further forward to catch the back water pump groove so that keeps things turning.