Relocating the rear differential 1.25” towards the rear of the vehicle on a 72 Dart

Guys, his springs are relocated to the frame so there are no front mounts to shim.

He could simply redrill the front mount holes 3/4" or so rearward. I certainly wouldn't move the housing to the front hole in the perch like he's proposing. You certainly could try, but you'd have to do the same with the bottom shock mount plate. Of course the driveshaft is then pulled out 1.5". That's kind of a lot and wouldn't sit well in my mind. It needs the support or it could beat the hell out of the rear bushing. Plus the rear shackle angle may be too much at that point and the shocks may even be hitting the housing too.