Look at www.car-part.com for used calipers. These will almost have to be in better shape than the rusted calipers on the truck. You could also upgrade to larger calipers and rotors from a newer model Montero or Montero Sport.

Most auto parts stores should have a the spring clip for the window crank. That style was used for many models in the 90's.

Mitsu # 6 - 98 6G72 Montero Sport, Locking Rear Diff, Aisin Manual Hubs, 31x10.5

Mitsu # 7 - 02 6G74 Montero Limited