Can I just pull out the xfer case and with some sort of simple adapter mate up dual toy t-cases?
If you want to keep that one word 'simple,' then the answer is easy -- and negative.

If you're willing to DIG into it, then it becomes more plausible... other folks have successfully stacked Isuzu transfer cases, with a good bit of effort. Putting a 'Yota case behind the Isuzu transmission has yet to be done, but is certainly possible. Machining a tailhousing/adapter to connect the two is sorta involved, vut all you're really doing is making precision measurements and transferring them to metal. If you have to pay somebody to do this, it will be expensive, but if you have time in a machine shop to yourself, all it should cost is hours...

IMHO, the adapter coupling for the shafts is going to be the bigger challenge. If you're near a major prototyping center (Los Angeles is GREAT for this), you can get ANYTHING made to ANY specs, if you have the bucks. Speccing it is a lesser challenge, here. Some folks have welded couplers together in the past, but that is pretty difficult to do with minimal runout and maximum concentricity. Still, this route is do-able, if you work with someone who REALLY knows what they're doing.

Going the dual Isuzu 'case that Rob metions simplifies the situation, since the transfer case for the Auto already has a female-splined input shaft that matches the output splines of Isuzu transfe cases.

I suggest that you get the Tera setup first, and identify whether you want or need further reduction.

Randii