Oh yeah--I see it now.
I just looked in the Series III workshop PDF files--(Part 4 section 37) and don't see any mention of a reverse lamp switch on the transmission. Same in Part 6 section 86--Wiring schematic.
The reverse lamp was most likely a requirement for NADA models only (just like the huge turn signal lamps and side marker lights).
I'm sure that someone out there has a NADA transmission out or accessable that can snap a pic of the mounted switch for you....
--Mark
1973 SIII 109 RHD 2.5NA Diesel
0-54mph in just under 11.5 minutes
(9.7 minutes now that she's a 3-door).