The engine surging is major, almost to the point of cutting out. I don’t think the Egr or vacuum hoses would cause it to surge on a slight incline. They are on my suspicion list.
This being a 74, the oddities for emissions begin here. I found an open vacuum hose and capped it no change. Pull the hose off and rpms went up. It seems this engine does not use a vacuum advance, only a vacuum retard. I saw what looked to be an engine emission label on the valve cover but it’s hard to read. I later found a similar label in a factory alteration kit. I guess I will have to but it and see what it is. I have also located the vacuum diagram on line