Need Help with Back-Up Lights

[BenReed]

Howdy.

I recently bought a 1970 C-10. The column and the hand-sawn hole in the floor for the after market 3-speed both basically indicate the truck was originally a column-shift. Question is, how do I correctly install a functional back-up switch with the current (after market) floor-shift setup, when the remaining (and disconnected) switch is for column-shifting? I'm guessing I'll have to get a tranny-mounted switch, but I don't know which one to buy, nor where to tie it into the harness.

...Texas doesn't require it to pass inspection, but I keep getting people on my ass while I'm trying to parallel park. Kind of killing the thrill of my new PS upgrade.

Thanks a ton,
Ben