I am using this site. because i am not in mood to do the manual math
https://www.5speeds.com/calculators/SpeedoCalc.html ( i changed to a different site)
https://www.inchcalculator.com/icwidget/?wtdm=w&wa=speedometer_gear&wb=MTE1NzA5ODQ3NTU= the two above want close to 15 but I think they are calculating tire squish and a more modern transmission.
site below uses basics
https://www.omnicalculator.com/everyday-life/speedometer-gear this site put 7 and 19 close
and assuming a 29.3 tire diameter. Let me know if this is correct for his tire size.
based on this math.
if he uses the 7 tooth drive gear Parts Group 4.343 GEAR, Speedometer Drive: GM# 3845073 1955-57 1/2 TON (3-SPD.) (exc. hvy. duty, O/D) (7 teeth)
and the 19 tooth driven gear it looks like this combination will work for his 3.07 rear end ratio.
I would expect the 19 tooth not to show up as correct for his tire because its assuming something other than a 3.07.
but the 7 drive to 19 driven to 3.07 to 29.3 seems to work in the calculator.
note:
after i did the math the i think if its 7 then you need a 14 to 15 driven . but 19 may be really close depending on tire size.
I would like to know he actual drive gear in it.
