A friend bought a "Dana 60" for $500. It was out of a 1990 Dodge Cummins truck, and was advertised as a Dana 60 with 3.54 gears and he bought it. After reading a recent post, I asked him to look at it closer and see what was actually stamped on it- 60 or 61F. He called back and it's a 61F. He had a 4.10 ring, pinion and carrier out of an '81 GM Dana 60 for it. I searched but perhaps not thoroughly enough... but what differences between the 60 and 61F interfere with parts interchangability?