How to Move Shackles in 3"

I wasn't going to relocate my springs inboard, but my 9" has been narrowed somewhere in its past, and to get my Prostars to fit, I had to. I only had 3/4" from the rim to the spring when it was in the stock location.

Anyhow, I have the Reilly Motorsports front boxes welded in. A-body inboard relocation boxes

I also have USCT rear shackle brackets.Mopar-A-Body-63-75-Spring-Hanger-Relocation-Kit-REAR-SHACKLE-MOUNTS-ONLY_p_165.html

I know the shackles can be moved without this kit, but I thought this would help. Now I'm not so sure. With or without the USCT brackets, I have to get those threaded inserts out of the way, or drilled through for the bushing that gets welded in for the shackles and bushings.

I read about using a hole saw. There's no way to pilot it except to weld a plate in the area and drill it, as was suggested somewhere. Not easy, either. I do have a 90* adapter for my drill, because the spare tire well is in the way.

I tried using air chisel to break the weld on the insert, but it's on there good.

I'm not even sure a hole saw would go through that insert.

Sign me,
Stumped in South Jersey