Advice on buying junkyard engines?

On the '97 Ford, did it hydraulically lock-up when it "blew-up"? Or rather, how did it "blow-up"? I ask only because of the known issues with the earlier 4.2's, and if this were mine, I'd try to find a later year engine and swap-over the accessories as necessary.

And as others have stated, it would be preferable to hear it run before putting down the cash.