86 b250 had the wrong engine control unit installed

Here's the story to this 86 b25o v8 van I'd like to buy: worked great for work, for years. Died, diagnosis was the engine control computer. They ordered a used one from a junkyard somewhere, had the part number, there were 2 to choose from basically, anyways when they received the computer in the mail it was the other one, not the right one. They installed it anyway, the van worked fine for a day, then died and wouldn't start... end of their story.

First I was thinking, great, get the right computer, along I go, good deal. But then I thought perhaps using the wrong computer might've really messed up engine. Any thoughts?

The engine will be fine. Just install the correct computer.