I see this scenario play out dozens of times a year since i work on these cars for a living. A guy buys a car with a nice shiny paint job and supposedly has rebuilt this and rebuilt that. In all reality what people are claiming is a rebuilt engine is just an 50 year old worn out engine with a coat of paint. Same goes with the rest of the car and the money starts flowing out like water.
To buy an engine that you know nothing about will send you down another rabbit hole.