Did you figure the gear ratio when you had the cover off?
Nope, I did not think to do that. I did figure the gear ratio from the tire size, and what I'm turning at what speed (2950 @ 70 mph). With the ratios available for a 14-bolt Corporate axle, I figure I have to have 4.10 gears.
Interestingly, the ratios on this Muncie SM465 with 4.10 gears and this size tires match up very closely with my Jeep with 4.56 gears and 35" tires. Up to 4th gear, they are nearly identical. The Jeep has two more gears, and that's why the Jeep is hitting close to 18 mpg, while the old Chevy is stuck at 6.3 or so. I'm working on that. I'm hoping a recurve kit in the dizzy will get me closer to 10.