I can think of a couple of problems that you will have to overcome to accomplish that conversion:
-The biggest one, the one you can’t do much about, is the small ½ ton outers, (bearings, spindles, and ball joint; the things that hold your wheels in place). I don’t know what is on the motorhome now, but I would not downsize, especially of your going off road.
-Going from TIB to TTB will give you a 2” lift.
-The 8-lug problem: Finding a Dana 44 HD TTB with 8 lugs and long beams will be hard to impossible as I am not sure it exists. A conversion kit will be expensive.
-According to the internet, the 44 TTB axle width is shorter (I think 4”)than the 50 and 60. Van frame rails are wider than on the trucks, so am not sure how well the coil buckets will line up or where the wheels will sit. Wheel spacers will exaggerate the weakness of the ½ ton outers. Lengthening the beams and axle shafts would be the appropriate fix. Measure carefully so you know what you are getting yourself into.
-For only a 2” lift, crossmember modifications will be needed. Cutting out the interference and reinforcing what’s left.
Is it possible: Yes. Would I do it: No
I think the 50 TTB fits the application much better as it has 1-ton outers.
As much fabrication as I think would be required, why not get something stronger? Ford would have used the 50 TTB in an E350. An SAS 44 or 60 would be the easiest way but probably require a 4” lift.
If we were talking about an E150 I would be much more enthusiastic (an E150 shorty, side barn doors, 44 ttb, 2” to 4” lift, 33” or 35” tires…… F#*k Ya)
Please correct me if I am wrong on any of this.