Efregoso, on your first question the easy answer is that you use all of the mounting brackets and accessories from the donor vehicle, or accessories (alternator, power steering pump, ac compressor, water pump) purchased new using the donor vehicle specs, and keep the serpentine belt system complete, as it was in the donor. An alternative is to purchase a new accessory drive system from one of the aftermarket suppliers - Holley has a new one, or March, Rocky Hinge, Vintage Air, lots of choices. Just google accessory drive system.
The second, converting the serpentine Vortec to V-belt, when you say you'd prefer to keep the V-belt drive I assume that you're looking at it from the standpoint of using your '72 alternator, power steering pump, AC compressor, etc? Assuming your accessory brackets mate up to the engine, and that they align with each other you'll need a new crank pulley and water pump pulley that align with your pulleys on the other accessories. It may be harder and more time consuming to swap back to V-belt, considering that your old brackets may not fit the Vortec? You're just going to have to fit things up and check alignment. Some of the aftermarket guys offer a V-belt package that's cheaper than the serpentines - check Rocky Hinge for an easy install kit that includes new accessories and is reasonably priced.

Good luck on the quest.