Go an auto transmission (T700/4l60E) and a Tacoma gear drive tcase.

The transmission we have is a Getrag, but not the type you were hoping for. It is designed SPECIFICALLY for the Japanese engines (metric) and does not have a replaceable bellhousing. More than likely would not be strong enough, and the stock Kia tcase is DEFINITELY not strong enough.

Next in line (possibly should be first in line) will be the diffs. These will need to be replaced with something stronger as both front and rear are "4 pinion" types (2 side gears and 2 spider gears) not 6 pinion that would be needed in the size we have for strength. SAS would be the go.

Spend an hour or so using the search button, most of this stuff has been "discovered" before.