Here is a
LINK for the Rocker Arm Assembly in the 48-51 Chevy Truck Manual. This should help.
The holes you can see in the shaft in that figure are for the attaching bolts. They go completely thru the shafts, of course, otherwise it would be hard to get the bolts thru. You'll notice that there are only 3 of them, corresponding to the three bolts on either front or rear shaft. I had to look at that figure for a while to be sure of what those three holes were for. There are 6 smaller holes on the bottom, so a total of 9 holes on the bottom of the shaft.
