I leveled and squared up the chassis on the frame table. Once everything was perfect I attached it with clamps so I knew it wouldn't move while I was modifying it.
The rear kick-up that was previously installed was not visually appealing, but even if it was unfortunately it was installed out of square and not symmetrical side to side, so this was a good opportunity to make it better.
Chassis jigged up on the rack. It's at "air out" height, but the jig allowed it to be unbolted and moved to a second set of holes that set it at ride height if needed.
View from the rear of how the chassis was to start with.
View from the front of how the chassis was to start with.
Took the big step and cut the rear of the frame completely off.
With the rear end set at the proper height with some temporary "wheels" of the correct diameter cardboard was used as a simple method of coming up with a better frame rail profile.
Rear view looking at the mock up cardboard frame rail profile.
If you look close you can see some vertical steel posts at the rear of the cardboard rail. These were installed before the original rear frame was removed, and gave me the exact position and height that I needed the new frame rail to end at eventually.