Coming from someone who has done a ZF to AW7x swap, the driveshafts are different in two ways: shaft diameter (1.75 or 2") and length. The length is the big one. Simply put, if you're swapping driveshafts, you need to essentially convert the trans. I think you'll spend a lot less time just replacing the u-joints (which are known for wearing out well before the transmission). The other thing to bear in mind ***and this is important*** is that the driveshafts are BALANCED. So, if you seperate the two halves, mark them first so they go together properly.