I have several mechanical-drive S-W "Marine/Diesel" tachos with 4,000 RPM max scale that were acquired as shelf-stale "NOS" still in their windowed display boxes for small money.
Around fifty bucks, on-average?
Cleaner and less gaudy than this one, and without the odometer:
Stewart-Warner Corporation Mechanical Tachometer with Fixed Mount PN: 82683 | eBay
They do have a wider needle and bolder, but simpler markings, may or may not have the same resolution.
Donor "guts" complete should be easier to re-case and re-dial (if need be) than creating new/altered works practically from scratch?
Dial alone just isn't that hard. One can create the "master" image as black on clear, then contact-print onto 5 X 7 mylar stock, friendly commercial printer or darkroom "bag" develop.
The resulting "negative" gives you a directly usable mylar dial, clear on black field. White stock or color film behind it - even opal Lucite, edge-lighted - and soon done. printed bass-ackwards the mylar stock faces the cruel world and protects the emulsion on the away side.
Waaay nicer than trying to directly 'puter-print the solid black.