You'll need another truck transmission. They're not the same. You'll also need to swap over the flywheel to one from a manual.
You'll need the pedal, linkage, clutch master, as well as a few electrical changes. Over on
http://www.nissan4wheelers.com, a friend of mine recently did this on his WD21 Pathfinder and found it easiest to just buy a donor truck and then part out the rest.