valvetrain noise 5.9 magnum

I don't think you need new heads, pull the valve cover on the side that's noisey and find the loose rocker arm. Check to see if the bolt that holds it to the head is loose. The best thing to do is get very familiar with the magnum valve train. The lifters are below the intake manifold, they ride on the camshaft. I think Moper is right on this. Replacing the lifters can be done with the motor in the car.