Pictures?
Is there an "80" cast on it somewhere, like a gusset/web on the housing?

This Dana site is suppose to help decode if you have the right numbers
http://www2.dana.com/expertforms/deabill.aspx

This thread has a picture of generally where to find numbers and what format:
http://classicbroncos.com/forums/showthread.php?t=114453

Grigg

•1951 GMC 250 in the Project Journals
•1948 Chevrolet 6400 - Detroit Diesel 4-53T - Roadranger 10 speed overdrive - 4 wheel disc brakes
•1952 Chevrolet 3800 pickup
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"First, get a clear notion of what you desire to accomplish, and then in all probability you will succeed in doing it..." -Henry Maudslay-