Hemi Fuel Pump Push rod difference??

The 426 hemi always called for a different Pushrod for the fuel pump then the RB and B blocks. I assume the difference was hardness, but does anyone know for sure? Was there a physical difference such as a groove, or stamp to identify the difference between normal big block and a hemi one? Thanks,

Another one of those mopar mysteries? No one ever wondered why two different part numbers?