Another thing to keep in mind is that tightening things up on the top end of a worn engine can cause grief on the lower end. I read this in Road & Track in the Seventies and I saw it happen to my brother's car. After rebuilding the heads the car began to burn a lot of oil.
A typically good article by Rob, although I must say that when I first saw the photo of the car in the garage, I thought, "you're looking in the wrong end of a Corvair for compression problems, guys!" 😄