You will need to find a sender unit as it contains the circuit board. That tach won’t have the sending circuitry in it as you have discovered. The board basically just fits in the can housing with a terminal board that allows all the wiring points in the circuit board to be soldered to and the various wire pickups from the car harness and tach to connect to with ring terminals. With a new board and wiring diagram it wouldn’t be difficult to rig a sending unit up. The housing sould be made of almost anything. You might place a WTB ad a find a used one in someone’s part boxes out there.
I would contact someone who sells the new tach boards (type depends on if running points or electronic ignition) and they should be able to help you with a wiring schematic. If that fails I can dig through my notes and come up with one. RTE is one popular place who sells new boards.
MOPAR Products
On the underside for mounting you basically need an appropriate nut and washer and the find a good short, stiff spring that will fit over the threaded shaft and it will be compressed by the nut and washer to where the tach can be moved between positions and detects with a little effort. There is also a nylon glide plate that screws to the top surface of the console and provides the detent action.
