My PO gave me a spare rear end when I purchased my truck which I finally got around to having a closer look at today..tried to compare it to the existing rear end that's on the truck now and both appear to be very similar but yet not identical..I took rear end back cover plate off (not identical) and other than patent numbers and similar gears..nothing looks any different. Is there a way I can ID the difference?? Also how do I determine the condition of each of these rear ends?? Worn/chipped gear teeth?? gear play etc?
Would appreciate some help. I would like to sell the one I don't use.

 

This is a Dana 41, the original rear axle in the F1. It's easily identified by the stamping on the right lower case ear.







The Dana 44 was next in line, production wise. It started in 1950, I believe. This may help with your two axles.