Many of the early M-151`s, Ford 1/4 ton miltary Jeep replacement, had drive flanges on both sides of the diff. Sure it wasn´t a custom diff. but a Ford diff. modified to mil spec.s (or produced by somebody for Ford). Trouble is, it´s an independant suspension type set-up. The internals may be adaptable to a stock, solid axle diff.
The Gamma goat steered the front and the rear axle, the center stayed fixed. The rear axle steered at a percentage of the front, it wasn´t a 1 to 1 ratio. Steering worked really well, most ways, but at a certain speed (somewhere above 50), the whole system broke down, along with vehicle control.
The best set-up 6X vehicle control, is the two front axles steering and the rear fixed, they use this set up, a lot, in Europe for mid to large trucks. A lot of narrow streets to deal with. Swedes pioneered this set up. Works well on shorter wheel bases (where the tires are close together).
A 2 1/2 ton military truck type setup, would probably drag the rear tires, on a shorter wheel base.