1.6 rockers please explain.

Tony covered it real well but I'll ad a couple things. Running 1.6 rockers should have no effect on valve train geometry. When talking geometery you are referring to how the scrub pad or roller on the rocker arm (depending on the style of rocker arm) is centered over the valve stem. As Tony pointed out 1.6 rockers don't change that part, they only move the pushrod in toward the rocker arm fulcrum to increase the lift ratio. They are generally a direct bolt on but as it was already pointed out you need to make sure you have the clearances to run them.