The 1960 truck shop manual I have gives a good discription of the new rocker oiling design.
Starting in 1959 the oil restrictor was inlarged from 1/16" to 11/32" to allow more oil to the rockers. At the same time they moved the groove inside the rocker 1/4" off center so it did not line up with the supply hole in the shaft.
Also they pinched off the rocker connector overflow tube. All combined, this pressurized the rocker system.
