Does anyone have experience running an alternator, water pump, and Sanden-style A/C compressor all with a single v-belt? If so, how long has the belt lasted?

This is how my Crestline came to me. Seems like a single belt would not be up to the task of running all 3 for very long.

1954 Crestline Victoria 312 4-bbl, 3-speed overdrive

The '57 Tbird I just got has been mostly sitting since a  Classic Auto Air system was installed on it about 12 years ago.  Now, in getting around to checking it out, it will run for about a minute, cold temps on the outlet hose, and then the single belt system will begin slipping.  Not sure if drag increases on the pulley from the compressor, too lose a belt, not enough belt coverage, or oil/ freon needed. 
Just sharing my experience to date. 
Ralph