Little oil to rockers

This past fall I replaced the roller lifters in my Vortec engine. The camshaft looked fine but the truck had a very loud lifter tick that started all of the sudden. This was not an exhaust leak. After the tear down of the intake system I discovered four lifters that were collapsed and the push rod seat discs were sideways in their bores in the lifters. I was going to just replace the bad ones but decided to replace all of them for extra assurance. After the eight hour job and reassembly the truck seemed to be repaired. The cam and lifters were quiet and I even drove it on a three hundred mile round trip. Upon return the engine developed a squeak that seemed to get louder. It had to be the rockers. I checked to belt and that is not it.
So off the drivers side valve cover and the rockers are dry. No flow. Mechanical oil pressure gauge (Eqqus brand) shows 55 PSI cold at idle and 20 PSI hot, taken off the block at the port by the distributor. The push rods were soaked in diesel during the tear down and blown out to be clear of debris. I remove some of the center rockers (four and six?) To make sure the guides were not binding with the tubes. After reassembly I started the truck and got a high pressure squirt from one of them and flow from the other. I bought some oil control clips but still the oil overflows onto the exhaust manifold. But still nothing from the rearward push rods or the front. (I have not looked at the passenger side.) Since oil flow is from the back to the front I may assume that I have not spun a cam bearing in the rear. The lifters are quiet and do not clatter about five seconds after startup, so they are pumping up. The distributor appears to be seated. There is no rocker adjustment, these are positive stop bolt down rockers. Could this be a push rod sealing issue? Are they the same end for end? They measure the same on a micrometer. Is assembly lube blocking the oil flow?

I am at the end of my rope.