Rocker arm ratios

Even with "true" 1.5, 1.6, etc. ratio aftermarket rocker arm, you won't get the advertised cam lift. You're losing a little bit through the inefficient angles between lifter, pushrod and rocker. But it will be fairly close and the engine will perform better.

I wouldn't consider stamped rockers for much over mild performance applications. Stamped rockers have also been known to get punched through by the pushrods when running too much pressure for too long. Aftermarket adjustables are a performance gain just from proper adjustments as well.