I would check the numbers{bolck and head},get an overall feel of the motor,quality and neatness of plumbing,bolt heads and wiring gives a clue as to how good the builder was,go as far as you can go then make a decision based on the total car,and the price your paying,I think all the other test are asking to much of a seller,it is a used car,some chance is enevitable,if some guy wanted to do a leak down and lab test the
oil,I would tell him to get lost,,these guys never buy,I have sold cars all my life,the guys who buys it will know when he pulls in he will buy,,the rest are wasteing time ,looking for a reason not to buy.my thoughts,,Tk