Is your truck a 4 cyl or 6 cyl?

There are plenty of used pumps on www.car-part.com

I can't recall the last time I heard of a power steering pump going bad. You should be good with any of the used pumps. Though I would flush some clean fluid through the pump before I installed it in my rig.

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

Mitsu # 7 - 02 6G74 Montero Limited