I am aware that with some unibody cars of yore' (Sunbeam Alpine and Tiger for one) the current way to test the present rigidity of the car is to measure the door gaps (top and bottom) of the car sitting on all four tires (doors closed) and then jack car up from the rear lift point and re-measure the gaps while the car is jacked. Any more than 1/8" variance can be a tell-tale sign that rust or collision damage has taken its toll on the chassis integrity. Reason I know this is that I am looking for a good Tiger and have read up on all the "buyer's tips".

However, those cars are going on 40+ years of age now...