I installed the Powermaster #9504 on my Dart Windsor as recommended by Ron McCall, I did have to re-clock it, and I did not use the optional shim that comes with it. As I recall, re-install will be easier on the 351C, and the #9504 is compatible with both 351C and W, same flywheel tooth count.
We need A/C where I am, but I tend to agree with you on possibly deleting in your case, except for possible resale considerations. But obviously, you still need to get the alternator pulley lined up. I recall some other thread within the last year of a similar issue, though I think it was on the DeTomaso list instead of here. I seem to recall the consensus was to either shim and/or grind down one or more of the bracket bosses to align, or a Pantera vendor may simply have a better bracket as Husker notes.