Ron. .
Maybe this will help clear up the problems you are having... .
I did a little digging yesterday with both my local Mopar contact and made a call out west to someone else I know who is in the loop as they say,LOL. The designation on your axles does not mean it is a "military" style axle as all of the axles are designated by the letters "M" in front(i. e. -M60=Dana 60,M80=Dana80,etc). The military axles made have a different axle tube size(which Skyjacker is correct about) and different bearing sizes for strength and durability. Also they are geared way different than any street production vehicle and if they "slipped" out into the mainstream public it would be immediately noticeable in the trucks performance. Now,one thing he did say was this,"It should not happen,but,mistakes do happen". No part number was given to me for the military axles as it was not a area he wanted to get into.
Take some measurements of your axles for me and send them over here. Use a dial caliper to check axle tube dimensions and make sure you measure the axle tube lengths from the center sections to the outer edges of the rears. I was also asked if you ever had a dealership do a summary report on it listing all your options and where is was delivered to as this may answer your questions.
Now on to a comment I seen earlier here about unusually optioned trucks. While Ma Mopar will tell you nothing unusual gets away we all know differently and their past shows this. In some of the shows I have been to or participated in I have seen some different combinations. The three that stand out in my mind the most are these...
-A 1996 Light Aqua Metallic Sport 3500. This color was a one year only color and I had never seen a Sport with it on and the owner had the build sheet to back it up. Truck is in Delaware.
-A 2001. 5 Flame Red Sport 2500 Loaded,Leather Camel Interior w/heated seats that was carpet delete with a rubber mat.
-The most recent one located here in Pa,A 2001 Quad Cab Amber Fire Pearl coat Sport 3500 6spd H/O. I was under the assumption that this one off 1/2 year color was never made in a dually and as we all know the sport option for this color is rare alone. It is a original truck,complete with all documentation, and the owner knows its a rare piece. The research I have done tells me it is a 1 of 3 built dually's in this color and from what I can find out it may be the only Sport 3500 in this color. I am still working on digging more about this one up.
Maybe we need to do a thread on odd or different trucks we have seen. Oh well,you know how to reach me if you need me Ron... ..... Andy