You're on the right track with the rockers. 3/4 turn to seat past zero lash is the minimum adjustment. You may be getting a little clatter if some of them are a little under 3/4 turn. 3/4 to 1 1/2 is the safe range. Did you check the number of turns on just one valve or on all of them? Each one is slightly different. Some of the rockers might need only the .030" shim. I'm doing the same thing to mine right now.