Replace with OEM. If you want to be a bit cheaper about it find one at the junkyard and take it to a alternator shop. should be a small hole in the wall shop and shouldn't be very much to get one cleaned up and working right. just make sure the junkyard one isn't oil soaked as thats the biggest reason for OEM failing in the first place. That said i inherited a '98 with a parts house alternator much like yourself and was having similar voltage problems. I as well didn't want to fork up the cash at the time either and just took the parts house alternator to the local alternator shop and had them run it and take it apart. He was ready to replace the rectifier, but once he broke it open turns out every single bolt holding the internals was loose. He tightened them up put it back together ran it on the bench and all was well. This was about 9 months ago and it's been working flawlessly ever since. But with that said i'm still keeping an eye out for a junkyard OEM unit to have rewound at the alternator for a few more amps. Also check the tensioning assembly on yours with say a personal mirror and flashlight and make sure its actually maintaining tension and the bolt isn't stripped or the bracket cracked leading to the squealing. Also check your ground mainly the two on the back of the AC bracket as you should have had to remove those to do the timing belt. Many a people have easliy forgot about those two grounds with reassembly of the timing job.
