Your concerns are all valid.
Rocker arms don't need much oil. In some setups, they are in open air. In other setups they only get a mist of oil from blowby. I guess you need to know, this is Ford's second attempt at building an overhead valve engine and the problems associated with the first attempt (the Y-Block).
Yes, oil tends to 'hang' in the rocker area so many FE folks add an extra quart or half quart when going on a long trip. Does it need it? Not really but that little bit extra adds a sense of confidence.
In the Y-Block days, oil was fed from the center cam bearing to BOTH heads. There was a groove around the center of the cam which was never deep enough. Consequently, the bearing would wear, closing up the groove which starved oil flow to both heads. There was another 'problem' because the oil hole was not a straight shot. It zig-zagged at the head gasket.
The rocker shafts were open to atmosphere which ended up bypassing oil when each rocker arm clogged the little holes with dirt/oil/sludge. This also lowered oil pressure. The problems were extensive.
FE rocker shafts are fed from two cam bearings. The oil groove is not in the cam but under #2 and #4 cam bearings. Click on the following picture for my oil modifications:
This ensures the oil has plenty of flow to the heads. Your head gasket is not supposed to restrict 70-psi of 300°F oil, at least not all the way. I restrict my rocker arm flow with a very liberal .093" drill. Some go down to .060". This keeps overall oil pressure up as well.
It's hard to say every gasket company maintained the same oil hole diameter because they change so much over the years.
Do not be confused regarding your head gaskets. I always check for a square corner in front and on top. Yes, coolant flow is shut off in the front and wide open in the rear of the engine because water takes the path of least resistance. If the gaskets were open in front, all the flow would try to get through the shortest route especially at idle speeds when coolant pressure is low.
I also block off the exhaust port at the intake manifold with a patch of shim stock. So all the exhaust heat goes out the exhaust. Be sure your heat riser valve is not stuck shut. I gutted mine with a torch and left steel in the holes.
Be careful with the shields, especially if your rocker arms are not adjustable. I simply left mine out but used shorter pushrods. You have a different ratio rocker arm which can drastically change the geometry of your rocker arms if the shield is removed. It's about .030" thick which makes a huge difference on the height of the stands. - Dave