8 years ago, I did the one-ton conversion and didn't like the camber change and bump steer.
So I fabricated upper control arm mounts out of mild steel 3/16" plate and raised the mounting points 2 inches.
I measured from the existing upper control arm holes and extended them upward, with reinforcing in places.
Also, I used the entire upper control arm from the GMC truck to make it similar in function.
If you look at the one-ton truck, the upper control arm is inclined, front pivot is higher than the rear.
I tried to duplicate this geometry to make it the same as in the GMC truck.

I am not a professional welder, but so far no problems with my welds. It has worked for 8 years.
It also helped that the engine was removed so I could weld on the inside of the frame.
As I understand the GMC frame is made from mild steel 1080, so heat treating is not necessary.

I raised the upper control arm pivot 2 inches. The camber change was better. But I had an unexpected problem
with the toe change. When the front end went down under braking the wheels would toe-in.
To solve this problem I had to lower the tie rod ends 5/8 inch so that the toe change was minimal.

If you look at the stock GMC knuckle, the steering arm is lower than the one-ton.
So either the tie-rod has to be raised or the steering arm lowered.

I ended up using bump steer kit parts from Speedway Motors to lower the steering arm pivot.
The parts I used are heim joints with 5/8" hole and 11/16" left hand threads to mate with a
Chrysler tie rod sleeve. That threads into the GMC inner tie rod. I used the Speedway Motors
tapered tie rod end extension bolt with a spacer to lower the heim joint 5/8 inch.

The tie rod parts are shown below:

Regards,
Bill

http://www.gmcmhphotos.com/photos/data/6085/medium/DSCN1557.JPG