First year up to a certain date, the oil holes in the rocker shafts weren't slot cut for better oiling. That can be and should be done. As mentioned, 2bbl and 4bbl used the same ones in a given year. '64-7 were solid cam with adjustable rockers. '68-9 were hydraulic cam with non-adjustable rockers. To convert from one to the other, include cam, lifters, push rods, and rocker arm assemblies.
