I was going to reply before I saw this post because ever since we had OHC Falcons in 1988 in our household, and anytime and everytime we have been subjected to Valvoline oil it has caused low oil pressure. My good mate works in teh engine reco game and in the early days he figured that out too with all the customer complaints. I'm not saying it is bad oil, but the Ford OHC sixes just don't like it. As for going 50W oil I'll say it again and again that just uses more fuel and costs kW. Use the quality correct weight oils and you will have no problems. My EA engine has done 290,000km over 21 years and holds great oil pressure using Nulon 5W/40 synthetic.

On another note, I thought with Bars leaks the idea is you flush it out after it works on the leaks, i.e. I thought you weren't supposed to leave it in there long term?

So did I with the Bars stuff but turns out the one I got it says to put it in after every coolant and thermo change. Its suppose to stop leaks and recondition the seals/gaskets. I was thinking I would have to drop the coolant and thermo, the old stuff you use to but not now.
The 20/50 is for a little thicker oil to protect while the head gasket is weak. Your right about the thicker oil but I felt it might need that little extra protection for now