Another think to watch out for on the axle swap is, at least on the half tons with which I am more familiar.
The 72 W200 should have a divorced 205 transfer case with lockout hubs and the 75 trailduster should have a married fulltime 203 transfer case with solid front hubs and an issue you will most likely run into is the 72 W200 front axle has a different pinion angle to mate up with its divorced transfercase so you will end up with a funky pinion angle and possibly some drive shaft issues if you put the the W200 axle with the 203 fulltime transfer case in the trailduster.