Worst thing that can happen to a motor, overheating is very bad. The one thing that really has the most impact on that is the driver. The biggest question that needs to be answered and only your bud knows that. Is how long did he drive it after it over heated?
That will have the biggest impact on where to start to looking. As mentioned above cracked head, blown head gasket, what you are describing does not sound real promising. Can you say compression test..