with 4l80e. you will need >>>>>>>>> new drive shafts , new transfer case mounts, transfer case adapter, and u may need to modify the floor , it will seat back, 4l80e is longer
but in return you get one very strong and reliable trans that can be made to handle 2000 lb torque. and if u ever brake down u can stop by at any trans shop and they got what u need.
with adapter and zf22 or 24. its very easy to do the job. no shafts or any other modification needed . interior stays the same . and it can handle over 300 lb torque.
i have dodge viper SHORT RATIO 6 speed manual Transmission so i can race with coyotes on the trail
i forget to mention that military spec 6.2 is more powerful that civilian speck 6.5 , so if u gonna use military spec 6.5, i wouldn't use zf trans. u get over 350 lb torque on that motor and if u put a turbo on it than u may get over 500 lb torque (more than cummins 12 valve 5.9 turbo ) military armored hummers have over 13.000 lb on them and still pull very strong. offroad