I think you'll need to pull the rear cover to find the axle ratio. It's usually be stamped on the edge of the ring gear (# of teeth on ring and pinion) or you can count teeth.
Kevin 1951 Chevy 3100 work truck Follow this saga in Project Journal Photos 1929 Ford pickup restored from the ground up. | 1929 Ford Special Coupe (First car) Busting rust since the mid-60's If you're smart enough to take it apart, you darn well better be smart enough to put it back together.