Rattle sound from passenger side valvetrain..

Did you roll the engine over by hand first to see if their were any loose pushrods? That should have been your first step. Removing the rocker shafts and inspecting things is good but with them removed you have no way of telling if something is loose. If anything, the likelihood of a rocker arm or pushrod being the problem is less than a lifter/cam so just pulling the rocker shafts and pushrods doesn't always tell you a lot.