Hi Chris -
You should be able to jack up the rearend and rotate one wheel a complete 360 degress and count the number of times that the driveshaft rotates. The driveshaft should turn over 4.10 times. For trucks with automatic transmissions, I would be surprised if they had lower (i.e. higher numerically) rearends installed, but I've been wrong before.
Also, if you take the rear cover off, you might be able to see numbers stamped on the edge of the pinion gear. If I remember correctly, 45-11 means 45 teeth on the ring gear and 11 teeth on the pinion gear. 45 divided by 11 = 4.10.
The 3/4-ton stock '49 rearend is an Eaton HO52 or an Eaton HO72. This is the same rearend used in '67-72 Chevy C20 trucks and the third member carrier assembly is a straight swap with your stock '49.
If you have any questions or need anything else, please drop me a line.
Good Luck!
Dan M.
[email protected]402-981-7917
