What LXguy said and;
I do not beileve the Magnum heads or intake will limit RPM in anyway except the prfile of the cam and the springs abilty to control the valve at high RPM's.
Shotpeened rods are a plus but do not hld a key to more power or RPM but the abilty to be there for any length of time with high power levels.
Edelbrock only has the RPM for the Magnum engine. MoPar has the M1 series in dual and single plane versions, and several types of single plane intakes. Hughes engines has a couple of versions as well.
