Hi... does anyone happen to know what the diameter of the pinion shaft and the diameter of the ring gear of a stock 1948 F1. I'm looking to replace the original ring and pinion to a higher ratio. Any suggestion on where I can find one?

Thank you,
Billy

 

Here is documentation on the Ford stock offerings with Ford part numbers you can use with specialty vendors:

 

Hi Billy

Randy’s ring and pinion makes a good replacement, I used their kits to move our F1 to a 3.54 and am very happy with it.

JB

 

The 48 through early 50 F-1s use a Dana 41 rear axle. Re-gearing an early F-1 has gotten so popular that a reproduction 3.54 gear set has been made. Part number 8C-4209, available from several vendors (example one here). Disclaimer, I don't remember if there is a carrier break in the Dana 41 that you need to be aware of before changing gears.