There is no doubt you can get a good one off the ground. There are many variables though. What is a good one to the person vending it may have unacceptable issues to a buyer. This can be based on things like the sellers level of knowledge being basically it runs so it must be good type of thing.

It will always be more of a gamble than an engine one has properly checked out. Then this can even be compounded by people selling engines that have the same ethics basically as a crook. The other issue is availability when you need it.

A mercedes rebuilt engine with perhaps fifty thousand miles on it wil usually sell for about the same dollars as a mediocre very high milage engine. That is another gamble in itself. As at a time of need what you find may be out of your control and more a luck of the draw. I always try to anticipate needs giving me some time frame to work in.

Several years ago I ran across a free mercedes rebuilt 617 turbo engine in New Jersy when picking up a car. I did not have the time or tools to pull it and had to walk away. The owner of the car I purchaed said he also owned it and the paperwork was still in the dash for the engine. It had little miles since installation. He was moving away and just wanted many things gone.