This has been gone over and over many times. My 305 was bored .060 over to 315, new flat top pistons, new cam extreme energy cam XE262H-10 218-224 Dur. .050 .462-.469 Lift, new headers, new edelbrock intake and 600 cfm carb, new valve springs, lifters. Puts out close to 300HP and 308 torque.