belt and alternator

[58Panhead]

I got a question I put a new alternator and belt on the ole girl and since then that belt just a squeels only for a short time when you first crank it up. I have a theory (and yes I have tightened it up and sprayed belt dressing) I had the belt replaced when it was in the shop and I replaced the alternator myself. The pulley on the new alternator is different than the old one. Do you think the belt may be for the original alternator and not this new one. If this is the case and I get a new belt that fits the new alternator will it not just start making that god awful noise on the other pulleys?