Question about Lifter Oil Gallery Plugs

All but one small block I have tore down had the plugs. I am building a 1971 318 right now that never had the plugs. Did the factory just forget them? Who knows. But I can say that is the way it came from the factory, as I got the car from the original owner, and that engine had never been toughed. Bearings looked fin. So there was never an oil pressure issue. That said I put them in. Why take the chance.

One thing I have been reading on is drilling a small hole in the plugs, and a small hole in the cam plate over top of them. This is done to help oil the timing chain and make it last longer. I am thinking about giving it a try, as every small block I have tore done seems to have an over stretched chain. I do not think they get enough oil from the fact. So we will see.