It is not practical to run 10.5:1 pistons in a pump gas car with cast iron heads. My brothers 67 Barracuda has AC and power steering and 300,000 miles on the engine and 400,000 on the car. It still runs like new. At one point I did swap the original 920 heads for open chamber 675 heads so he could run regular gas, but I think I had 68/69 pistons in the short block which are .030 higher in the block. He did not spin tires, but it would cruise @ 100 mph all day long and top out around 140 mph with 3.23 gears. He got 20+ mpg and with a certain carb about 30 mpg @ 60 mph. He ran a stockish Commando replacement cam and a 340 double roller timing chain. With either engine you choose, the cam would be the key for both power and driveability. Think 340 or smaller.
