There is no chance, no where, no way, no how that I would go to the trouble of putting an engine in any vehicle that was starting with 200k miles on it. NEVER.
But I guess I'm just funny that way...
And yes, the Explorer engines were so well tuned that if treated properly can easily go 300k and probably more. Not sure how many made that milestone, but some of them could have.
Even if you expect to get 100,000 miles out of, and only drive it 5,000 a year at the most, you might think that's 20 years worth of fun. But it's still only a "maybe" at that. Engines hate short trips and sitting as much as anything else. So that theoretical extra 100k might just have gone out the window with a low use Bronco.
I guess I'm just lazy and don't like to take engines in and out of Broncos for bad reasons.
I hear what you're saying, that it sounds like you would not have someone else do it and would be doing it yourself for the first time. Looking at it that way I can see the reasoning for just putting it in and crossing your fingers.
You have seen and heard it run, and have tested it and no oil leaks or smoke. It sounds good, and if the alternative is lots of work at rebuilding, then I think you have your own personal answer in this case. Just clean it up and put it in.
Still not what I'd do, but it makes sense here. Not necessarily the wrong decision, but somewhat of a gamble nevertheless.
If the Explorer is still even drivable, I'd spend some more quality time and mileage driving around in it. Just to be sure the engine is going to run the same in 1,000 miles as it is idling in the driveway.
If that's not an option, then toss that coin!;D
Paul