Basically heads dictate horsepower, not cubic inches. Cubic inches dictate at what rpm you will run. If you read his first post, he intends to put a gen III Hemi in the car and wanted to know if the 273 was salvageable. You are wrong about quench between 273's and 318s as well. 273's are usually about -.020 to 0 deck height. My experience was quite different with 273s. I would never run a 318 over a 273. I would run a 318 if that was what I had, but I kept 273s and 340s. Passed on 318s and 360s. Nothing I have ever had was "original" stock. A 67 Barracuda would have 10 in drum brakes and a dual master cylinder with a Commando 273, even my brothers 67 273 2 barrel Barracuda had those brakes. Just to let you know, I'd build a 289 over a 302 any day of the week.