.....after a lot of online research and speaking with American Autowire, I found my answer. Well, as I already knew, the manual trans floor shift trucks in 72 had no neutral safety switch. So from the factory, there was a dummy plug the factory installed into the factory n.s.s connector above the steering column to bypass (jumper) the n.s.s circuit. These are apparently no longer available although it would be super easy to make one.
Now as far as the backup light switch, the diagram shows the 18 gage dark green wire is doubled up on the back of the fuse box allowing two paths for current flow. So in short, all the factory did different with the flor shifted models is install a different engine wiring harness that puts the reverse switch on the tranny instead of the column. Buy the m/t specific harness, plug it in, and you are good to go.
http://1.bp.blogspot.com/-dmJl1v1q_t...t-Lighting.jpg