I converted to an alternator and I can tell you that I ran into a problem with the aftermarket bracket. I bought the proper bracket, but the not converversation kit, so I had to fabricate a back support. There is one company that sells a true conversation kit.
The bracket alone won't do the trick, unless you have a block newer than 63, I think. If I wouldn't seen the Powergen sooner, I may have tried that route all the benefits of the alternator but the cool old look of the original.
Hope this helps