If you don't have roller bearing rocker shaft assys, you not only don't want to restrict the flow up there but possibly add to the flow-this has been done many times back in the sludge days(non detergent oil) by running exteral lines to the upstairs from the oil pressure sender port and entering under the valve covers then hooking to the hollow shafts.

In the non drilled solid lifter blocks I have fabbed individual lines to run to each tappet boss for additional oil plus also ability to run hydraulics.

Layer aftermarket rods don't have adquete side clearances plus don't have the oil squirters to oil upper areas of crankcase-----

These mods over the years have made it even more important to have proper and adqueqte drainback to the valley