Throwing belts

[78BO]

Hey guys,

So when I installed my engine I found out that some of the brackets didn't quite line up right because I went from the Gen1 350 to a VORTEC top end. I had to cut the alternator bracket to get it to fit. Everything looks like it lined up. But whenever I stomp on it it throws the belt. What gives? I know I'm not the only person that has a vortec set up. Is there another bracket that I can buy? I also bought some new chrome pulleys (crank and water pump) but they seem to wobble (out of round). I think I'm going to go back to the old pulleys and just repaint them. But back to the brackets, I also found out that the rear A/C bracket wont work either because the vortec topend. So is there any place to pick up brackets that will work?