Couple points. First, don't trust anyone's pushrod length recommendation. Get an adjustable length pushrod tool to measure what you need. And measure both intake and exhaust, preferably on every cylinder. Not that uncommon to find you need different lengths. Second, shaft rockers are a whole different animal. They will set you back about a grand or more but they do away with guideplates and hold the rockers perfectly square to the valves. Very nice to have if you want to spend on them.
http://www.jesel.com/valvetrain/index.php/rockers/sportsman-series
The magnum rockers have a reputation for lots of problems. Actually, lots of Comp parts do. For about a hundred bucks more you can get a set of full roller style rockers and will have better luck. Scorpion, Crane and Trick Flow all have good reps. All are supposedly Crane design with Scorpion making them for Trick Flow. Crane uses a newer design with a different oiling relief pattern on the rod end. Whatever way you go make sure to check clearances. Binding on the stud is a big one to watch for.
http://www.jesel.com/valvetrain/index.php/rockers/sportsman-series
The magnum rockers have a reputation for lots of problems. Actually, lots of Comp parts do. For about a hundred bucks more you can get a set of full roller style rockers and will have better luck. Scorpion, Crane and Trick Flow all have good reps. All are supposedly Crane design with Scorpion making them for Trick Flow. Crane uses a newer design with a different oiling relief pattern on the rod end. Whatever way you go make sure to check clearances. Binding on the stud is a big one to watch for.