Rocker Arm Shaft Differences

[zgerbic]

I have been disassembling some stock rocker assemblies and noticed a couple different designs. Also noticed another just looking through images of FE rocker shafts. There appears to be shafts with a single oil hole, two same size oil holes, and two oil holes where one appears to be opened up to about 1/4" part way in. What is the application and years used between these three configurations?

Thanks