Since no one answered you... I dont' know much about the 3.8s. But I recall hearing somewhere that you would have to swap out the bellhousing if you changed it on a 5.0.
they're different in that the V8 T-5 can handle the more torque, than the V6 T-5's. I'm not sure about the bellhousing though. I would think they would have to be changed, because the V8's have a bigger flywheel.