Before replacing anything further, I'd recommend getting a can of Silicon Spray Lube. If you can replicate this nose with the truck parked and running try spraying the drive belt and see if the nose goes away. If not, liberally spray the drive belt and take it for spin and see if it still make this nose.
If the nose is still there, invest a few bucks in a mechanics stethoscope (click this link mechanics stethoscope
) to see if you can narrow down where this nose is coming from.