Pulley's and belts

Is there a primer/sticky somewhere on pulley sizes and maybe conversation to serpentine belt's. My current configuration is; single belt driving water pump and alternator. I am getting ready to add rack and pinion power steering (Saginaw pump) and before the build is finished air conditioning. I know I can't run everything on one belt. The crank and alternator have dual pulley's, I will need to buy a pulley for the pump. Also have given some thought to going to a serpentine belt. I've done a lot of reading but don't seem to find a lot on it. Maybe I just don't know how to filter my results.

Thanks,
Bobby