I bought a 105 Amp marine alternator from BG Electronics to charge my 3 trolling motor batteries, crank battery (all m-30's) and run livewell, bilge, stereo, etc. I have a Stealth DC on-the-fly charger that eats 40 amps + whatever the crank battery and system need. I have a Vortec 350. The original 51 amp stocker had a two-belt pulley, but the shaft diameter was different, so I couldn't use it. The single belt set-up squeals at start up and at take-off. I have a serpentine crank pulley that came with my Craigslisted Vortec. I was thinking of finding a serpentine alternator pulley to mate-up with my new alternator. Am I likely to find one that will work? The new alternator is the older design, and I have seen there are many shaft diameters used, some with and without keyways. Are there serpentine pulleys that fit older GM alternators with proper clearence, and line up with the crank pulley? If I go the serpentine route, do I really need to also install a tensioner / idler pulley(s) or is that just for ease of setting tension and change out?