Replacing belts
 

I found the belt for the ac hanging under my truck, so I changed out all the belts today. Now I have a terrible whine though, the alternator tensioner does nothing, so the belt is pretty loose... I think that makes up most the whine, but i've noticed after revving the engine the whine dies down, then if i put the ac on the whine starts up again. Do I need a new ac compressor? And how the hell do i get the alternator belt tight

Alternator-if it is like my 92 P/U-One bolt is the pivot and one bolt is the slider. Loosen both, use your hand to move the alternator til the belt is tight, then retighten bolts. If you get them reasonably tight and it still squeaks, spray w/ some belt dressing.

the pivot is broken I guess, I can only tighten the one on the slide. I've tried pulling the alternator pretty hard and then tightening at the same time, but it's still not very tight

What do you mean the pivot is broken? The alternator, bolt, bracket?