O/D Push Button??
I have done two of these one in my 64 dart GT and the other in my 66 dart Wagon. If you have the switch that is all yuo need. Just get the wiring harness from the trans and part of the wiring from the switch. I have the book you will just need 12 volts to turh the sol.off and on. The light is on when it is not in O/D and one of the other wires goes to the ign switch to light up switch. Look in the lower left hand corner of the picture and you can see you swith on the floor.
Pm me if you need more info.