Speedometer - Free - Speed Limit Alert with Map, HUD and GPS Black Box Recorder by Stanislav Dvoychenko
https://appsto.re/us/NmhqH.iGreat product. Free for basic, couple of bucks for upgrade. Perfect for checking out accuracy of speedo and odometer.
The more teeth you have on your 'driven' gear on speedo cable, the slower your speedo reads compared to your actual true speed. The drive gear is the one on trans tail shaft. Contrary to op's thoughts, I believe you need a driven gear with fewer teeth, not more.
When does the ground war begin?
