Rocker shims = NO rocker shaft oiling

Inertia,
Yeah I remember the Isky Anti Pump ups. The reason for so much internal lifter travel is to allow for production tolerances....& maintenance. Heads being milled during an overhaul &/or valves being sunk with a valve job.
You certainly wouldn't want to bottom the lifters out completely, but on an all iron engine you could certainly go to within 0.010" of bottomed out & still have internal clearance. Even if the clearance went solid, it is not going to wipe the lifters/lobes because all that would happen is the valves are held slightly of their seats; probably cause some rough running because the valves are not seating.