You can raise the rockers or move them with shims. But you still have to set the preload or lash.
YES raise first then order pushrods
"Rockers are what usually come apart and then the pieces fall down into the motor. I have seen many of rocker pieces ruin good motors. Spend the money now or spend it later."
OLD are you referring to needles?
IMHO for most builds the stock Magnum and AMC rockers will work just fine
if you do get roller tip rockers remember the arm lengths are all over the place
so set your geometry (raise the fulcrum height- its going to be about the radius of the roller tip, get the right length 7/16 studs then see if your witness stripe from the roller is in the center of the valve tip
