I have a Stewart speedo head that I suspect wasn't original all to the car, given the pickaxe hole in the firewall and matching dash technique. All I have is the head...and wonder if it's worthwhile n putting back in.
I can run the coupler with the drill and get a speedometer reading, but no change on the mileage or trip counters.
I suppose the rest of the bits would be pretty expensive. I could attempt to disassemble, to see what's up inside. I've never popped the case off one vefore, tough.
Power drills, hole saws, saber saws, electric sheet metal shears (my pair will cut 18 gauge steel). We get so spoiled. Oh, the techniques people used to use to cut a hole in sheet metal! (Hammers, chisels, blocks of wood.)
No doubt, your speedometer was probably an after-market one (most were). I would probably put it back in, even if I never hooked it up. It is part of your car's history.
Original factory or dealer installed options were usually neatly done. Owner installed accessories sometimes were not. You can likely clean it up a bit by carefully heat and shrinking the metal dash using an acetylene torch, hammer, and piece of metal flat-stock. To neaten it up even further, make a simple bezel out of aluminum sheet. Easy to do. My coupe was from the San Francisco hills area, and had a pressurized gasoline tank with a hand pump to improve fuel flow. While not badly done, the fit and finish was not ideal. So I made a bezel out of a scrap piece of aluminum I had. Cut, fit, filed, and extremely fine sanded. Looks much nicer now.
But that is my opinion.
Drive carefully, and enjoy, W2
Your speedometer was made for a 1926-27 Ford. It has the colored odometer dials to indicate when you are supposed to lubricate the car. Unfortunately, the odometer dials are made of pot metal and have swollen. These dials make the speedometer un-restorable, and if you continue to turn the input shaft with a drill, you will ruin/destroy the speed drive gear. Sorry for the bad news.