72 Dart, mini tub, narrow rear, spring relocation

I,ve done the mintub,3 inch spring relocation.I alos moved my rear back 1 inch to fit a 29x15x12 slick.

Is moving the axle back as easy as moving the point at which the front mount of the leaf spring is mounted. Couldn't I just essentially move the leafs to a more rearward mounting point in the front box, then the rear shackles would just swivel back to compensate? Or am I missing something. Thanks for all the help and time. It really sets me at ease because it seems as if I have all these ?'s in my head. Thanks a million!
-Paul

Here is the project