You dont use a gear puller on the alternator pulley...
It has a conical wedge holding the serpentine pulley to the alterntor shaft. The shaft is not tapered but the hole in the pulley is. If you take the nut off and look at the shaft, you can see the ~1/8" thick end of the wedge with the split in it. You have to get a socket or piece of pipe big enough to go around the wedge but fit inside the face of the pulley. You then beat the piss out of the pulley and it will loosen the wedge free. Its best to put the alternator face up on a piece of wood with the back on the housing where the shaft is supported directly on the wood. This will somewhat absorb the impact of the hammer whacks and hopefully keep you from FUBARing anything on the case. Make sure the threaded post on the back of the case is not taking the brunt of the hits, its insulation WILL break. Then just getcha a normal v-belt pulley and bolt that ***** on there, it is just held in place by friction, no wedge involved.
Straight from the GM manual, right?
Seth Stewart '04
2000 Suburban DD
1995 F150 SAS - Needs more work to sell
1998 GMC pickup - sold
2003 Yukon XL - wrecked/motor donor
1975 Scout - TBD
1976 Scout - parts truck
1972 IH 1310 dually - TBD
196? Scout 800 - 302 roller