Well, if you are using the original parellel rear springs, mostly what you need are the spring perches to weld to the new axle and some shock mounting brackets to weld on there too.

I looked at Speedway, and they carry the formed perches for the axle, and also have some 3 hole shock brackets for the housing, too.

But it sounds to me like, if you were looking at a Butches kit, there must be more to it than just these few parts?

I might be missing something, but with parellel springs you won't need panhard bars, or any of that, so most of your stock shackle stuff, etc, should work, and it would be a simple matter to fab up the rest.