I love all this talk about such a simple topic. My advice is to tap the oiling holes in the heads, and screw in a plug with a 1/16" hole drilled in it. Simple and the cost is next to nothing. Also, if my center oiler had less than 25 psi at temperature and less than 60 crusing, I might be checking my bearings.
If my memory serve me correct, the stock 57HV pumps pop off at around 85 psi. If while assembling my motors the rods and mains were a little on the big side (.0035 / .0030) I would replace the spring in the
oil pump with a 100psi unit. Of course I'm talking about the center oiler engines which mains and rods are at the end of the line.
Back to the real topic here, I think restricting
oil to the top end only keeps excessive
oil from getting into the valve covers and prevents sucking the pan dry.
Don't know it this helps, but that my two cents worth . . . . .
Steve W.