[BIG BLOCK JIMMY]

Thank you all for responding. Here's the back story:
I bought the truck from a classic car dealer whom fixed/ added newer parts to include a steering rebuild kit, i.e. tie rods, ball joints and all that good stuff. I'm 99.93% sure they did not do any type of alignment.
The leaf springs were old and I do not believe they messed with them. The steering has been horrible since I bought it. I installed a new gear box and swapped out the rag joints for u-joints and pretty stuff. Steering still horrible.
I knew all the bushings were shot, so I ordered a new 4" lift kit from skyjacker along with a truck load of other parts (monster trans and T's transfer case) and had a "custom shop" install all of it.
They did catch that someone previously installed the rear blocks backwards and they mentioned that the front axle is as I stated ~1.5" out of square. By that point they had my Jimmy for over a MONTH and I just wanted it back!
As I laid under the jimmy attempting to figure out how I was going to make the FOURTH set of headers work (whole other nightmare) because the passenger side tubes were hitting the rear of the front passenger side shackle bolt....hence the new ORD shackle and so on.
The original shackles were old as grease and tired. I could force the springs to appear almost straight, but the axle obviously isn't going anywhere.
I measured the frame over and over, all the body panels are lined up, very little rust to hide anything and it all looks original. No signs of previous damage.
I placed a jack stand ~4" behind the rear shackle which held the front tire 3" off the floor, then put my floor jack just on the inside of the shock mount and slowly raised it until the pressure was off of the rear shackle. I played around with several different lift points to see if I screwed up the jacking procedure, but it wasn't moving where I wanted it to.
I guess I need to remove the entire spring for further investigation.
Sorry for the long post, I tried to make it short