with enough support parts a 3.6 should drop right in without much pain and suffering, i've herd the 3.8 is a different beast, not seen one to confirm though, they are basically the same motor from the head gasket down, the rest is just induction differences and maybe a little wiring, the body plug will be pretty much the same, depending on year they sometimes move a wire position (like the ac compressor lead) but the plug will match up
all america wants is cold beer warm cat and a place to take a poop with a door on it