OP: Read the sticky
Deffinatly if you are going to put that big of a change in a v6 I would put in a new drive shaft, because a v6 drive shaft just wont work with the amount of power that is going to be put out. Great Idea though! Hope it works!
WTH are you talking about? Shafts are the same. Yokes are the only thing that is different. Are you mistaken for rear ends?
Foxes had an even smaller diameter driveshaft tube than 94+. On my 5.0 I have an aluminum junkyard driveshaft smaller than the FMS one. With 275 bfg drag radials and 322 torque to the wheels I drove the hell out of it at the dragstrip and it's fine.