Blocks and internals the same?

I second the suggestion for Magnum heads, They have a more efficient closed combustion chamber, Better ports with lots of velocity and the 1.6 rockers. You can pick a used set up for around $200.

CarCraft built a 318 using the Magnum heads with no porting, KB flat top pistons, zero decked for 10:1 compression, a Comp Cams 280H cam 230 @.050" 480 lift (512" lift with the mags 1.6 rockers) a Mopar M1 single plane and a 750 cfm carb. It dynoed at 400 horse power on westecks dyno wich is probably closer to 350-375 on anyone elses dyno.