On T&D single shaft rockers the pushrod length(+ or - .090) is very critical due to the oil slot in the adjusters for the ball end pushrods Not so much on all the single shaft Harland Sharp, Crane and all the rest of the ball and cup rockers I've used They can be within .150 of perfect and still work well
Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)
Not so much on all the single shaft Harland Sharp, Crane and all the rest of the ball and cup rockers I've used 
They can be within .150 of perfect and still work well 