These pictures may help illustrate the situation.
They're shims I made for my truck after I too welded the spring pads on in the wrong orientation.
PICTURE 1 PICTURE 2 PICTURE 3 They're about 1/4" thin on the little end and close to 3/4" on the thick end, over the length this makes for 6° taper.
They have 3/4" diameter pins that fit well the holes in the spring pads, the pins are welded. Then 1/2" holes are drilled to fit the spring bolt head.
You're talking about a shim that is about 1 to 1-1/2" on the thick end, that's a lot of change.
Before I knew anything about driveline angles I thought it'd be OK to just remove one spring pad at a time and weld it on in the right place (moved over an inch to suit) keeping it parallel to the other pad not yet removed. Then repeat on the other side.
This was not at all a good plan when swapping axles... I later found out.
So that shim at 6° was my solution and not a bad one, but 6° is not a lot of angle.
Were I in your situation now with 12° or so to correct I'd start over with the spring pads on the axle tubes.
Grigg
