Reverse switch

Just recently purchased the truck listed above with the 5 speed manual 4 wheel drive. Unfortunately not sure of the transmission model. Was about to get the truck inspected and noticed the reverse lights not working, bulbs are fine. Searched the forum for the reverse switch location and on my transmission, there is no switch on the side just forward of the linkage. I saw a wire hanging down which I assumed plugged into the reverse sensor. I used a jumper, and the reverse light illuminate. But again, no switch! I noticed a switch located on top of the transfer case with nothing plugged in. I remove the switch and attempt to plug it into the unused connector and they are not made for each other.