The dual transfercase set up is usualy the range box section of an NP203(front half),that is mated to another T-case(usualy NP205). Off road design has a kit that does this. It works best in long wheel base rigs like, fullsizes or extended WB rides,as the total length of the trans,range box, adapter and final T-case is around 44". This set up gives you 4:1 low and 1:1 high so you can crawl or fly. [url=www.offroaddesign.com]
Take a peep at the site, LOTS of info.
The divorsed TC eats up room, as it has a short drive shaft from the trans to the TC, easy to fix, easily upgraded. The married TC has a fixed adapter between Trans/TC. These are strong for the most part, but break this and you will grieve. This is my educated opinion, there are many schools of thought on this though. On most Jeeps there is not enough room for dual TC. <img src="/forums/images/graemlins/cheers.gif" alt="" />