dusterdoug,
nm9 is pretty much right on the money here. Unfortunately, small block Mopars, including the Magnum engines, use a very short rocker. The small block Chevy roller rocker is a little longer, and being a roller, needs to be raised a bunch to have proper geometry. That makes the stud too short, not too long. It also means the roller is right on the edge of the valve tip, if not falling off altogether.
You're not alone here. Even a Chevy has these issues when using a roller rocker on an otherwise stock stock replacement head. See the attached pics. Because the problem is the same as a Chevy, the fix is also the same as a Chevy, and it's likely to depress you. The rocker stud holes in the heads need to be relocated for acceptable valve tip alignment, and big block Chevy screw in studs need to be used to allow the rocker to be raised enough for minimal sweep, which is true geometry. That centered sweep has been deligitimized so many times, I can't believe it's still being advised.
Your choices are narrowed down to, as you mentioned, going hydraulic with stock rockers, or, the extra machining work I mentioned above. The extra work is the best approach, but stock rockers and a hydraulic cam will probably be cheaper. Once again, it's not in the rocker, per se, but in the fact that head wasn't designed for a roller rocker, even though the roller is a better performance choice when properly set up.
Notice the pattern is not perfectly centered, but the roller barely moves across the tip of the valve. I couldn't move the stud hole enough to get it perfectly centered, yet it has perfect true geometry and will run circles around an engine with a centered sweep that is, in many cases, three to four times that width. And, it will live a lot longer.
