273 Rockers on a 1971 340

The ball oiling mods are for extended high RPM use, like racing. The stock oil restriction system gets even more restrictive at high RPM's so mods have to be done. For more mundane use they are ok as is.
The banana grooves are easy to add; a cutoff disc on a Dremel or a triangular file will do it. Just keep the groove ends within the wear area of the rocker body to try to avoid creating extra leak points. BTW, the pressure inside the rocker shafts is very low, like a few psi, so this is not super critical.