I have seen that if you have the fully splined 2wd 4L80 output shaft, that it can be cut down to work with a transfer case and stock adapter. I bought one with such a configuration that already had the tail bushing lube port plugged. I went to take some measurements to cut the output shaft to size and i noticed something concerning. The adapter was already mounted to my NP261 transfer case and i noticed that the input only sits about 5/16" recessed from the mating flange face. Looking at the transmission output shaft, i noticed that there is a tapered section nearest the transmission. It sticks out about 13/16" total from the flange face. Seems as though the snout of the TC input would hit on this larger diameter section of the trans output shaft before the adapter mates up to the trans. Pics for reference.

5/16" recessed from flange face, not boss fit.

Tapered section of the trans output shaft I think the TC input will make contact with.