Do you have a mechanical oil pressure gauge and how is pressure at various operating conditions? If this is a car you intend to keep and drive seems like getting motor done completely and to your liking maybe in order. When I did my motor, it turns out the valve guides for the head had a tap ran through instead of properly sized by previous owner. My buddy who does heads, showed me how much clearance the valves had. So he custom ordered bronze guides and installed them, with an otherwise stock valve job. I provided new valves. Generic stuff you can buy was too loose in his opinion. Once done, I did the valve and spring install under the guidance of master engine builder. Many older block have restrictors in the oil passage that many now think are not necessary/wrong. Might be worth the time and expense to do it right, especially for a car you intend to drive a lot.

As far as the tube conversation, mine are originals, but I was told it was OK to use gasket. Helps make the heat range a little hotter. You just can't torque it down to some of the high values I have seen in after market head instructions. The whole oil in the tube thing seems like a red herring to where is the oil going. You will always get some leakage into the tube when the plug is removed. But the head is sealed off when plug installed properly.

Before you pull the heads inspect your intake manifold to head fit once it is removeable. China wall gap large or small. You can't see all ports but you can see some for fit, plus gauge the gap. I imagine if it was bad, you would have drivability issues which I do not think you have.