I don't know if anyone has come out with anything new yet, but about the only way you are going to power both the rear axles is if you user the drive train from a duce and a half(military truck). I sure can tell that is a 360 and 727 trans, color and shape of oil pan and shape of the trans pan. My van was a 73 and i was under it alot changing things. I also had a 54 Willys CJ3B i towed behind going to the mountians in Colorado Springs. Wanted to do a painting on the sides of the van towing the jeep and would you beleive i named it Voyager and the jeep Voyager 1.
The plan so far for driving both rear axles:
Leave the transmission as is. Used the front half of the current NP203 and with a ORD Doubler, add a twin sticked NP205 Transfer case behind that. The NP205 will have a second rear output added using NP200 parts. One rear output will go to the forward axle straight, and the second will go to a pillow bearing on the shoulder of the front axle, and then via a UJ to the rear, like the Kiaser setups.
This setup will give me a High/Low/Super Low 4-1 crawler ratio, as well as 2, 4, and 6WD. The info I have says that that the modified Np205 with dual output will allow me to put one of the rear drives in N for the street.