Hey Chris,
by taking a view on the E350 frame video, there's something that would be great to get more info:
Tranny mods for 4x4
I know that you've the kits for 4r100 and the different one for 5r100, or so...
Would be great for us followers to get more details on the needed mods and what is compatible and what's not. e.g. normally you've the tranny that was stock for the engine- but it could be useful to switch to an more reliable 5r100 if the old tranny is done. + a 5 speed gives a better fuel effectively.
What kind of mods must be done in that case regarding shifter/transfer case etc...
You are covering the axle swap mods in this thread really great and of course this is the most important part of the 4x4 conversion but its probably an easy one for you to get us up to speed in this.
For me its maybe more interesting anyway, as I need to swap my E4OD probably. But that's a different story probably, as I've a borg warner transfer case.