Hey,
How'd you do the hydroboost steering? Did you use an orbital valve to control the hydraulic cylinder? This is one area I haven't adventured yet, so please excuse my obvious ignorance. Also, for the 4-link, did you use the exsisting torsion bars in any way, or did you scrap everything and start from scratch?
I'm more of a transmission guy, so if you need anything done on either the Allison or 4L80E you are probably running in that, just let me know. There's a vendor who gets me parts and kits really cheap. I have an '06 2500HD with the Allison T1000, and once you put a transgo shift kit in one of those, they are bullet proof. It is an unbelievably easy task as well.