How to sell a used engine?

Ok guys, I've got a question and want some opinions. I bought a '69 Dart that someone put a 360 in. I haven't ran the numbers to see what year it is and don't know a whole lot about it. I was told by the kid that I got it from, and the kid that owned it before him that it was a fresh build that was .060" over but that's about all they knew about it. I can see the 360 "J" heads on it, it has an aluminum Edelbrock Victor 340 Air Gap intake, and an electronic distributor. The Holley that was on it was dumping fuel so I pulled it off and put an Edelbrock 600 that I had on a truck at my dad's. The carb had just been rebuilt by myself and when we put it on the 406 Chevy in my dad's truck it would idle good and was tuned well enough to drive around but not perfect. We had to hotwire the ignition system as the wiring was cut and spliced everywhere. I just wanted to see if it would run before I pulled it so didn't care about the wiring. I got it to start and run, but it would never idle. Seemed no matter what we did it would sputter and die when you let off the throttle. Granted, I'm fairly new to tuning at all, but the guy I had helping me has been around it a lot longer than I have so he knows a little bit.

So here's my main question. There's a member here looking for a 360 to get his Dart going. I know this engine runs, but don't know anything about the internals or if it may have other issues. I don't want to sell him something that's trash, or is going to cost him a bunch of money. How would you go about pricing something like this? Is it basically a core engine that may have new parts? Do I take it apart to look at everything and the put a gasket set in it so I have an idea of what's there? I have no confidence in what the previous owner's have told me and I want to halfway know what I may potentially be selling someone. I'm just curious how others may go about this. Thanks.