Not sure about that swap. If you are able to get some type of adapter to link the 4.6L to your current drive-train (i.e. your tranny) i don't see any need to swap rear-end or even driveshaft. I am not sure on the torque gains but I am assuming they aren't significant enough to change your whole drivetrain. Don't set my word in stone, hell i wouldn't even bet on it like I said not sure about this swap, never done it, never know someone to do it. Just thought I'd chip in with my opinion. Good luck!