replacement engine for 2001 B4000 4x4

[Pontiacpreacher]

I recently lost the rear passenger timing tensioner, and I figure if I've gotta pull the engine to have those parts replaced, I just as well put in a lower mileage engine. Current engine has 125k on it. Looking for compatible engines. I'd prefer to just drop an entire unit in, without swapping intakes, exhaust, wiring harnesses, etc. Am I stuck with finding a 2001, or are there other years from other models that are a direct drop in?

2001 B4000 SOHC
4x4
manual

Forgive me if I've left out pertinent info. All of my auto experience revolves around pre 1965 stuff.

Thanks for any advice you guys and gals can send my way.