It has been a while since I installed the Delco, but I remember that it was necessary to put an "S" bend in the original upper bracket. Instructions to do this came with the SWEM kit. I think the instructions are also on the SWEM site (http://www.intelab.com/swem/). If the bend is not put in the bracket, the alternator won't line up properly, and this would lead to problems for sure.
You also need to go to a little longer belt. Just bring your old belt to a parts store and ask for one a little longer. I had to exchange this belt once or twice before I got the size I needed. The SWEM instructions tell what size belt to buy, but you might have to go up or down from that, especially if your lower bracket is not a SWEM.
I don't remember which Delco I bought, but it is the one recommended by SWEM and is the most common, one wire (built in regulator), alternator that was used on all GM products in the 70's and 80's. But they are available with different bracket hole locations. If you think you need a new one, check out the SWEM instructions or email Ron Kwas there, I am sure he will be glad to help. But, I think all you need to do is put a bend in your upper bracket and get a new belt.
Tom