magnum cam and valvetrain upgrade

I want to upgrade the cam, valve springs, and maybe rockers in my 360 magnum. I bought the longblock used and the previous owner said he put a cam in it but couldn't remember what. The cars been great, got it to do 12.8 @ 105 mph in the quarter mile. The motor does have stock valve springs which i also want to upgrade. What do you guys recommend without disturbing the heads as far as upgrades?

70 dart full steel body, TTI ceramic step headers, eddy air gap, holley 670,manual steering, manual brakes, A904 W/2800 stall,3:55 and a locker.

I would like to keep the redline around 6000 RPM.