squeals and pulleys

[Larsonlegacy]

Greetings,
This is my first thread on this forum, and I hope to be able to contribute more in the future. I have a 1968 GMC C2500 with a 396. The truck was purchased by my grandfather new in 68 and has been passed along so I know quite a bit of the history.
I finished a full rebuild of the engine this month. (bored to ~ 402, new everything including alt, water pump, harmonic balancer) i was hoping that the engine squeal that it has had since I was a child would be remedied with the rebuild..., no such luck.
I have read several threads on squeals and pulleys but I think my situation calls for a little more info. The squeal happens around 2500 rpm whether its under load or just revving and continues until rpms drop. I know its the crank/wp/alt belt. It is also damaging the belt on both sides (not top and bottom). Diameter of crank: 7.8" lwp: 6" alt:2.7" interesting thing is the part number stamp on the WP pulley pulls up a '72 corvette with 350? So I am sure that pulley is wrong. My father remembers something about having the crank pulley replaced for some reason, but cant remember details. Does anyone know the original sizes of the pulleys that this truck came with? The pulleys are lined up as best I can tell. I have no idea where to start and funds have been almost depleted by this point. So I can't throw pulleys at it blindly.

Thanks!