Viperwolf has a handy Bronco correct speedo gear chart.
Transmission does not matter, only diff gearing and tire size. And the big unknown, which DRIVING tooth count is on the transfer case output shaft. Either 7 or 8 tooth, and that makes a HUGE difference in which driven gear you need on the speedo cable.
I would be surprised if you couldn't get them from Ford parts. Most Ford model specialty parts places (mustang, cougar, etc) carry them. There are 2 types of gears, those for auto trans and those for manual trans and transfer cases. You want the manual trans type. Its shorter.Where are these gears available for purchase?
There is also left and right hand spirals. Take your old gear with you and match it.
Without knowing which gears you have now the best I can say is 2-3 more teeth on the driven gear.I have 33" tires. Speedo shows about 74 and gps shows 65. Anyone know which color gear would I need to get these closer? I don't expect perfect but anything would help.
Thanks!
First thing I would do is figure out what did the grinding.So if I dont have the old gear and the new gear teeth have been grinded down, what do I do? ha. 32" tires and VIN says B90 under axle