I agree with the post above, and the importance of the question of 'what is the use for the engine/car'; different uses result in different solutions.
FWIW, the production 318's were NEVER 9.2:1, early or late. The only ones that got into the mid 8's actual static CR were the Magnums. Even the early LA's were high 7's or low 8's. It is a 'theme' all across the board at the time: use some theoretical minimum chamber volume to compute and advertise CR. All the numbers I have run through say that Mopar exaggerated CR by .75 to 1 full point into the early to mid 80's.