Glenn,
I'm not sure! It seems to me that the line for the rockers is on the tail end of a large galley for the lifters. I haven't heard of the larger internal passages plugging before. If you could backtrack until you found pressure, then, using a air gun to help you, go forward until you found a blockage, you might have a chance.
Between a can of Brake-Kleen and a rubber tipped air nozzle, you should be able to 'strike oil' somewhere.
The fact that you have a car engine with hydraulic lifters, keep breaking rocker arms and aren't able to get oil to your center oiler seems too coincidental to me...it's all in the same general area.
I did see a note in the service manual that cautions about the gaskets on the oil distribution valve. There are two gaskets and they must be installed in a specific order. Keep us posted.
Stuart
