Daniel,
Looks like a great project. I want to recommend one thing, I have not done an SAS, but I have helped a few friends. The Trooper frame is designed for independent front suspension. Notice how short the frame height is were the suspension was attached. The IFS frames are designed to carry the load at that point. When you cut the IFS off and add a leaf spring, you have put half of the front end weight at the extreme front of the frame. This results in a large bending moment on the frame at a very thin point, i.e. a lot of stress in a critical point. Also consider that your engine mounts right in the middle of this section. Previously the engine was supported by the IFS cross member, but now the frame will carry all the load. I know there are many successful SAS's out there without frame reinforcement. I am a mechanical engineer, and I would recommend some reinforcement in this area. I would add some deeper plates on either side of the frame, that will increase the depth of the frame, and then boxing in the bottom of the thickened section. This will make your frame immensely stronger,and make the finished rig drive better, because you will have more rigidity in a critical area. I think that thin frame section is a weak point in many SAS conversions. Just my two cents, so take it for what it is worth, but I think you will get more life out of your frame if you reinforce this area. Good luck with the project, it looks like a lot of fun! I wish I could come across a set of one ton axles! I will admit, they would find their way under a Jeep not a Trooper, but Troopers are great rigs.