47-59 Rear leaf spring swap issue

[TX3100Guy]

I purchased a set of front multi-leaf springs that were listed as 2 1/2 inch drop from stock and rear multi-leaf springs that were listed as 3 inch drop from stock. The process of swapping out the front springs was fairly straightforward with minimal difficulty. As a result, I assumed the rear would be about the same.

After getting the wheel and shock off on the passenger side, I then made sure to take all the tension off the spring my having a jack under the diff. When all tension was removed, I took off both the threaded bolt on the front of the spring and disassembled the shackle on the rear and easily removed the mono spring. Once I got the front new threaded bolt lined up and installed, I used a small bottle jack to line up the rear of the new leaf spring and was able to get the shackle assembled.

It was at that point that I noticed that the bolt/nipple that is mounted at the center of the leaf spring and is intended to be centered into a shim, as well as used to line up the lower shock mount bracket was off center. While the leaf spring was lined up front to back on the axle properly, the center of the leaf spring was three inches too far forward of the axle. I tried lowering the axle to meet the spring and even tried raising the spring assembly up with the bottle jack to see if it centered.

The other thing I noticed was that the rear shackle was pitched forward rather than rearward like the drivers side. I'm not sure if that accounts for the three inches, but at that point I was frustrated and removed the leaf spring.

What am I doing wrong or what haven't I done that I need to, to get this leaf spring mounted?