One thing you can do to lessen the amount of adapters needed and keep superselect is to use the original superselect case from the early Gen 2's with the smaller motors. These cases will bolt up to the underdrive but you will have to drill for clocking.
The NP231 and 241 cases will bolt up to the Mitsu transmission, but you will need the Jeep tailhousing and to modify the pulse gear. We are swapping the Rubicon Rock-Trac NV241 transfer case into Lloyds '95 SR, Here's a link to his build thread. you might want to skip toward the end somewhere as we are just getting the T-case in now and it's a long thead. Lloyds build


Here's NathanC's thread on installing duals into his Gen 2 Twins

Here's My '88 build with Duals, Not much info here but i can post up more and add some pics. B4R and gear driven case