I'm glad to find this old post still active.
I'm getting into an old 455 boat engine that sounded like it had a little man with a hammer inside. For a long time now I have been hearing about these restrictors. It was killing me to see them in the mains. I just flat wouldn't do that. It's crazy. It sounds like a real half *** fix to me. Just from a logical thinking standpoint. The cam bearings will drop the oil right into the crankcase so that's not a problem. the only thing I would concider would be the pushrods. The thing I would def do is deburr and enlarge oil return passages at this point.
My boat engine teardown revealed main bearings scored like you find brake rotors. I think it's never been machined before and think it will come out. This engine ran at 6000 in our boat for verry extended periods of time. If it were running out of oil, I believe this engine wouldn't have lasted through a whole tank of gas. The engine blew a head gasket and was hydrolocked in the morning. The heads pulled and gaskets replaced and oil changed.... note: you can't get to the drain plug in the oil pan so you have a tapped hole in the side of the oil pan that will let maybe a quarter to half inch of oil remain undrained. In my mind oil floats on water so if there was still water in the pan it would be at the point below this tapped hole and remain in the engine along with the fresh oil. The next outing didn't last long and came back knocking. I don't think it was due to oil starvation. Nothing seems hot or siezed up. My experience so far. We put the original engine back in it along with the "C" heads and crower cam. It dosn't turn 6000 anymore but does go about 5700 and no issues yet.....