I'm not understanding how the glow plug controller and IDI tach need the TCM. The tach runs through the TCM, but doesn't need the TCM to work. Also are you going to use the factory cruise system from an older truck or the super duty? I think the Older cruise may pull signals through the TCM, but doesn't need it. I'm guessing that I'm missing something on how this ties in with the superduty electronics.
When I cleaned out the wiring on my 89 after removing the E40d the wiring diagrams for a manual truck showed tach, VSS, etc going directly to a component, but on the auto truck they went through the TCM first.
Super cool build. I'm enjoying it greatly!