Well, the Pathfinders used a rear disc I think (at least some of them did). Seems the componentry should be out there then for doing a rear disc conversion. I don't know what to tell ya about doing a 2wd-to-4wd front brake conversion -- the whole suspension's different obviously. I doubt anything would bolt up the same. The 4x4s do have dual piston calipers, that's kinda cool.

If I ever thought I'd own a vehicle with dual piston calipers, I didn't figure it would be a Nissan truck!
