Decoding 1974 posi gears

[kanuck]

Is there a way to ID my gear ratio by code so I don't have to take the rear cover off?
Original code from the fender is C-80. It is a 1974 14 bolt corperate with the corporate 10 bolt front.

This is from the parts truck I picked up last week. Was a one owner truck that was parked in 2001 and the owner passed away in 2008.

Bought it mostly for the doors, but it has a great dash pad, tach dash and full interior trim. Cab looks decent for the most part, will need the inside rockers redone as there is rust on the underside. Truck was cleaned up and repainted in the early 90's. Frame is rusted out totally in the rear.

Other question is, "will it be a pain in the butt using a 4x4 cab on a 2 wd. I know it has the tall tunnel, but it also has cab lights. Any other differences I should know about?