I have a paper '99 EWD (Electrical Wiring Diagram) book. Would a scan of those pages help you?
I can tell you the two position detection switches on the J-shift T-case are for the ADD system. One side does 4H and the other does 4L. If I look at the truck I can remember which is which. The switch on the 5-speed trans is just for the back-up light. The dash light is controlled by the position switch on the front diff. That's all you have to do underneath.
As far as the J-shift 5-speed goes, the lever engages the TC, which closes a position switch, which closes the ADD relay, which enables vacuum to front diff actuator which engages the diff and closes the switch that turns on the dash light.
Forgive me if you knew all this.