I have always used Motorcraft belts. I change them at 100K to 125K and have always had a good experience with the OEM belts.

 

i think the alternator brand was world wide. and the belt i bought was dayco. as i said no more squeal but i did notice last night when it was realy cold again there was a whirring kind of noise going on up there. tonight it wasnt as cold and i didnt hear the noise. maybe the belt just needs to break in or maybe thats i noise im stuck with when its cold. either way ill take that kind of noise over a shreaking squeal anyday. i cant wait to trade this truck in on a diesel!

 

I've seen similar issues with Gatorback belts. They seem to stretch out a lot more than other brands for the first couple thousand miles of use. However, once they break-in, a tension readjustment will usually clear up any squealing.