Speedometer evaluation?

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I have 2 67 model rally speedometers here just like yours with tenths wheel worn completely out. Both need only that 1 part that I don't have a source for. ...
I had Sammy (@ MuuMuu101) make me a tiny gear on his 3D printer, maybe he could make you a 10ths gear? would have to send him a CAD file of it, but there are plenty of gears over at tinkercad.com. just look at other projects, find one that has the same tooth count and scale it to what yours would have been.