Not sure exactly what you're trying to accomplish, but you can add another switch and keep the factory one operational. Connect one terminal of the new switch to a ground, and splice the other to the orange/white wire from the factory OD switch.

If you're just wanting to put a switch in a more convenient place - can't figure out why Dodge put the switch at the bottom of the dash - I'd suggest swapping in the shift lever from a newer Dodge truck, which has the OD switch built in. That is one of the best mods I made.

 

A while back there was a post on putting a switch on the end of your shifter. it requires the type of switch that wprks like a horn switch. one touch will do the job. you dont want a permanent type flip on/off. Make sence?

 

I got it from Radio Shack and used a rubber "foot" that I got from the hardware store. I tapped into the orignal wiring so both switches work the o.d. All you need to do is momentarily ground the od to toggle it on and off.