AC Belt Squeaks But It Is TIGHT?

[ghackett1]

Hey guys, quick question, when I switch my a/c on in my 71 pick up with a 402 engine, it squeaks like crazy but if I play with the gas a little it will go away until I stop and try and take off and it will start shrieking again. I checked the belt and it seems plenty tight. I do notice that it is a narrow type belt (I replaced it) and seems to fit way down into the pulley. Do you think a wider belt would be the way to go so it would catch the sides of the pulley better, or whatever your thoughts are I'd appreciate because its HOT down here.