So, the ambient temps dropped back into the 60's today, and I could not duplicate the problem. I did look at the wiring & tighten the spade. Not sure how much that matters when it's relying on the round pins on the bridge connector. I took that apart & cleaned both sides with contact cleaner. I'd really like to replace these pins. Does anyone know what series/brand they are (Yakazi, Furukawa, etc.,)? The oil pressure gauge worked again after this, so I have to consider that these contacts are less than ideal now.
I could see that there were issues with the hanrness along the frame rail, so I stripped out the ground wire to the alternator, which had clearly overheated at some point. Thankfully it hadn't shorted or melted through the insulation of any other wires besides the smaller grounds that splice into it. The connector at the inner fender was not tight at all. One of the heavy gauge black wires goes/comes from inside the cabin, not sure offhand what circuit it is grounding, but the connection was not good at all.
made a new ground cable for the alternator, and tied in the 2 smaller ground wires that were previously connected into a separate ground. At the other end, I separated the grounds that came from the cabin & added a separate eyelet
Alternator end
wrapping that up, I ran the engine & immediately smelled gas - #3 injector hose clamp was not fully tight at the rail. I will need to redo all those at some point. I hate the open slot hose clamps, they are not appropriate and always cut into the hose