8 3/4" Questions

I have a 73 Duster and it has an 8 and 1/4" read end under it, stock except for a Posi unit I had installed. It has the 5 x 4.5" pattern with the wide drum brakes. I really want to replace it with a 8 and 3/4" rear end. Out of what body (A, B, C or E) would I be able to find the rear end that is the easiest to swap into my Duster? Would I be able to keep my same drum brakes? Would I need to by a new parking brake line or will I be able to keep the one I have now? Also is there any differences between 742 and 489 cases? Is one better then the other? I would want to have the 8 and 3/4" rebuilt, what companies would anyone recommend on rebuilding it or that sell axles, ring and pinion gears, etc, for it? I am looking at getting a Detriot TrueTrac Posi Unit, there was a magazine article on it recently where they tried to break it. They were not able to and I will not be doing what they were doing to it. Are their any opinions on that posi unit or any others? Does anyone have any opinion for gear ratios for a car that will mainly be a street car (some highway driving), but that I will race it sometimes? I also plan on getting a 4 speed automatic for my Duster as well.

Thanks for any help you can provide.

Seth