STUD1Y
+1y
you could do a six link.
two links on the front axle, two on the rear axle, and a 2 links between the axles with a center pivot, much like the articulating axles on a car hauler. you just need to make sure they can flex independently.
it will be hard to find a axle small enough for the truck that is set up to be a tandom drive axle. You'll probably have to have one made, or shorten the shit out of a medium duty truck rear end and respline it for regular axles... who knows... lots of work!