The magnum heads are 94 and later 318-360 heads. They have 1.92" intake and 1.62" exhaust valves, closed combistion chambers and 1.6 ratio rockers. They flow better then a stock X or J head and the closed chamber allows you to build for good quench wich will make the motor more efficient and have better torque and throttle response.
These are the heads from the Mopar Muscle article. They use KB pistons at zero deck and a .039" head gasket thickness to set quench distance. The heads were used with no porting, A comp Cams 280H cam and a M1 single plane intake. It made 400hp on Westechs dyno but is probably closer to 350-360hp in real life. I also think a Magnum RPM Air gap would be a better intake for this motor.