Hard to say, it's a little like the "ran when parked" statement. The buyer has no guarantees of anything until a full inspection is done and even then, it's parts, not an engine yet. It can get very expensive very quickly if unseen defects show up, the original owner didn't finish the job for cost reasons. The buyer can't even be sure all the parts belong together.
Check some values for the individual parts such as head, engine cases, etc. It could help you arrive at a price.