Offset spring hanger stud replacement

[69GT]

I am in the process of installing a Mopar Peformance offset spring kit on my Dart and have a couple of questions. While I am doing this I would also like to bump the rearend back 1/2" to give some additional tire clearance at the front of the wheel opening so I had a couple of 1/2" thick spacer plates made. With the spacers in place, the factory installed studs on the mounts aren't long enough to securely tighten the nuts on far enough. I would like to know if anyone has ever removed the studs that are pressed into the spring mounts and replaced them with either new studs or bolts. The way the mounts are welded together the two studs on the one side are underneath the side of the bracket and don't have enough clearance to come out. I suppose I could somehow cut them off but then I'm not sure I could get new studs or bolts to slide in their place. Has anyone else had any experience with this situation and if so, how did you handle it?

 

['64 Cuda]

I plan on moving my axle back a bit too, but probably more like an inch to an inch and a half. Haven't decided how much yet. My plan is to drill new holes in the perches & shock plates & then just set the new holes down on the spring bolts.