Mating a 4L80E to a NP205
I asked some questions a while back about doing the above and I wanted to post a follow up thread with what I found and what it takes to make it work the easiest.
You want to start with a 4x4 version of the 4L80E. I used the later model from a 98 model truck. The transfer case will need the 32 spline long input setup like is used on 87-91 trucks with a TH400. The input can be changed if you dont have this already.
You will need a 3/4" plate to install between the transmission/transfer case adapter. This is due to shaft depth and the difference in transmission and transfer case slightly different case diameters at the mating surface. I found someone to buy mine from, but a reputable machine shop can easily build it. This will make the adapter mount clear the pan and will make the output shaft depth correct for the transfer case. This will make the overall length right at 2.2" longer than a TH400 setup. You will have to lenthen any braces to the tcase and the shifter so that it is in the correct location in the floor.
Hope this helps if anyone searches in the future.