I received my donor from Copart, bought is last week from El Paso - more info in my build thread. Short story, I bought it from the photos and a short discussion with Copart to ensure it had everything that I needed to satisfy my build requirements. Got it home and so far, so good and was exactly as I expected its condition to be.
If you need a car with a working engine and trans, it will be a little more expensive and harder to find 'just the right car for the right price'. If there is doubt about the functionality of the engine, look for another car - or find someone who has a TC engine for sale and don't overbid on the car with a non-functioning engine.
It took me a month to locate mine, and only then was I able to win the auction on the second time around when the first one did not pan out and the car was relisted a couple weeks later. Just for conversation - I may have the TC engine and F35 trans in my donor car to sell at some point, I still need to confirm it's full functionality (just got it home 2 days ago). I have a new crate TC engine and new F40 transmission I will be using in my build.
Communication with the forum members can help by trolling the local ads that you may not have visibility to. Adam and Lonny from the DF Team can also assist and my have something on hand in Red Oak.