I agree completely that a Ujoint converted E Series is a great set up and far easier to build/buy than making a Synro equally capable off road and/or towing, ok maybe even driving!
But as with everything, personal preference is a huge part of vehicle choice.
My basic plan is this.
Diesel Multivan non syncro base (for smog purposes)
Rear mounted LS Small block, maybe a 6.0, but most likely one of the aluminum block variants for weight.
Custom adapter to mount a 4l80e with the bellhousing against the OE "firewall". This adapter will basically space the flexplate, torque converter and trans about 10-12" away from the back (now physically the front) of the engine. Sort of like a short version of the torque tube setup on a C5 vette or a 928 Porsche, etc. Designed for rear axle compression travel clearance.
A 3.8 geared Atlas connected to the back err...."front" of the trans.
Rear (front) output feeding a centered flipped ARB'd Dana44, hung on a simple radius arm/coil spring setup like an FJ80, as low as reasonable to run 31's, anything bigger and it misses the point.
Front (rear) output feeding an extra offset flipped ARB'd Dana60, again hung on a simple Radius arm/coil spring setup.
Disconnectable swaybars front and rear. Setup to allow for reasonable travel and articulation. Nothing crazy.
All the power and reliability you could ask for in a 4500lb van
A real overdrive automatic trans
A real lowrange t.case for true 4 wheel drive, the Atlas allows independent FWD, RWD, Locked 4wd
lockable basically bulletproof front and rear axles (when compared to the stock design CV's, even with 930's all around, BOMBPROOF!!)
The "flipped" regular rotation axles, will reverse the direction of rotation so you go the correct direction in gear (always a plus) and give you high mount pinions for good Dshaft clearence.
The room is all there without any serious floor mods, and it will sit at the same height as a normal "lifted" Syncro
About the only down side is that washboard roads may be a little less cush, as you loose the independent suspension all around.
And if you can keep your foot out of it, fuel mileage over 20mpg is very realistic. With 350+hp on tap, when you need it.
When I do it (way down the road) it will have quiet exhaust, and A/T tires. Nothing extreme or flashy. Cruising down the road total stealth to the Layman. Hit the trail and it will out "wheel" a tire lifting locked syncro without even putting it in 4wd or locking the diffs.
Still in the early planning stages, but once the bugs are worked out on paper, I'll start collecting parts, and a base for the build. I have a 6.0 in my garage and it will fit no problem, even under the engine lid.
"One often meets his destiny on the road he takes to avoid it" -Oogway
What would Bruce Campbell do?