I worked in a Desoto/Plymouth dealership when I was in my teens (a long, long time ago). In the 50's. Anyway, the dealership had a used car lot and they would, during the night, have an electric drill attached to the transmission end of the speedo cable running it in reverse. It worked then and I suspect it would work now.

Dan
"I think I can, I think I can"
My Current Truck: http://ILovePortTownsend.com/54Toy.htm
My Last Truck: http://ILovePortTownsend.com/Truck_files/53.htm
My 59 Vette: http://ILovePortTownsend.com/Truck_files/59.htm
My High School Vehicles: http://IlovePortTownsend.com/Truck_files/late50s.htm