Maybe everyone already knows this EXCEPT me, but...........
I have a car (KP61) with another cars engine and a donor transmission from a third unit with an electrical system made from scratch...You get it.
I had NO speedometer.
I found several GPS round, stock looking speedometers on Ebay. Bought one for just $58. I cut a blank out of plexiglass the size of my dash panel and popped it in with a SUN tach simply hooked up to my coil and a temp gauge hooked up to a sender in my upper radiator hose. Painted the panel black and wow. Pretty impressive!!
It works GREAT.
Fully instrumented dash panel. With night lighting for about $120! And no issue routing a cable. Just a few wires and a hidden antenna.
Just a tip for anyone driving around looking for a speedometer or a cable to fit your custom length sized or no longer available cable.
There are also digital and "heads up: display types. And some of them are under $30.
Give one a try.