Srt-68 Barracuda
Could you use an encoder wheel modified to fit on the axle? Enough lines on the wheel could = 160,000 pulses in a mile.......pulse output qty = number of lines on encoder times number of revolutions of the axle per mile.
IE if the encoder has 200 lines on the face and rotates 800 times in a mile you would get 160,000 pules per mile.
I used them on electronic tape loading machines to count the number of times the hub rotated......that in turn translated into how many feet of 1/2" vcr tape goes into the cartridge....very simple solution to how to determine footage....same principal could be applied to your situation by a good technician.