On the Saginaw pumps SB and BB have different pulley spacing. Are you sure you have a BB pump?

In general, mixing different generation pulleys and brackets doesn't work. I tried it with a '78 BB core in a '70. What a mess. I wound up getting a '70 style WP housing (most aluminum repops are), PS bracket from Bouchillon, Sanden compressor and mount from Bouchillon and matching "with AC" 2 groove fan pulley. The rebuilt Saginaw BB pump from the '78 fit fine. Bouchillon has some good pictures on their site.

I'm not sure how you would run a "with AC" setup without compressor. The compressor and alternator share a pair of belts and "with AC" alternator mounts are unique with different sweep for adjustment. One option is to go ahead and install the compressor. With no power to the clutch it will act as idler. You can run that way until the rest of the system is ready.

I've attached a pic that shows part of the setup. Note I went with the giant 100A '78 core alternator after the square back and matching brackets from Bouchillon didn't have enough juice for my application.