how involved do you wanna get on this project? have access to machining resources? basically, no matter what route you go, dual tcases is going to be a lot of custom work. nothing out there existes for a bolt together option for the Isuzus.

running a toy tcase on your isuzu automatic? i'm pretty sure there isn't an adapter out there for this. i'm also pretty sure the input/output shafts are probably different diameter/spline count, so it would probably be more than an adapter, but a new input shaft for the toy tcase as well. again, no one makes this, but with enough research, it could probably be machined. i don't know enough about the toy parts to help you any more.

another option? dual isuzu tcases! slap another auto tcase on the back of the one you already have. This project would follow the same lines of what myself, Chad, and Dan have done, but instead of using the integrated tranny/tcase (MUA5), you would be mating to another auto tcase. Process would be about the same, two hurdles to overcome, adapting the two together, and then clearing the front output of the first to make way for the front driveshaft to hit the second. but the beauty of this approach is that if you remove the output flange of your tcase, the spline shaft is a perfect match for the input of another isuzu automatic tcase.

look here to get some ideas.

-Rob