I was thinking about doing it. At one point in time, I had a lead on a GM NP435 transmission, which were only used in 2wds. I was thinking about swapping the stock 35 spline mainshaft out for a Ford 31 and using a Ford NP435 4x4 tailhousing, and then bolting on a Ford NP205. I don't even know if the above is possible, but it sure is interesting.
However, the transmission is no longer available and GM NP435's aren't exactly easy to come across. That and the fact I'd pretty much need a '78-'79 Ford parts truck with a NP435 and a dana 60 front (read: $$) also helped kill the deal in my mind. EDIT: Oh, and the Dodge D60 I got for $150 pretty much helped push me in the "keep it simple" direction.