Very late to the party, but why not machine a relief on the transmission side of adapter to depth of the adjacent socket head cap screw, and put a stud in the starter, and use a nut on the stud?
I’m going to swap in a factory locker into my 2000.
Based on my research, it seems like all that is needed is the additional wires in the rear frame harness. Pre 2002 LXs seem to have all the wiring in the main chassis loom already as there is...
That truck isn’t worth the effort. The rust flaking here is likely everywhere. Missed SteveH’s post-beat me to it. But I have a truck from VA that’s way way cleaner than this.