EGR was new in 1973 … older vacuum schematics will not include EGR vacuum plumbing.
My advice is to collect all the necessary components first, test them, make sure they are functional, make sure the diaphragms don't leak, etc. It makes no sense to attempt to make it OEM if ALL of the parts aren't available to do so. I understand some of the emissions equipment is unobtainable. The EGR was still plumbed in my Pantera when I purchased it, but it didn't function properly, it stuck open when it was hot … prevented the engine from idling. New EGR plates for a 4300D carburetor don't grow on trees.
Talking about the 4300D carburetor …. the '73 4300D carburetor knocks engine output down by 90 horsepower. 90 HORSEPOWER!
The overall purpose of the EPVS (anti-over heating controls) was to reduce engine idle speed by 100 rpm upon rising temperature. Coolant pumps are engine driven. Does it make sense to reduce engine speed, and pump less coolant, when an engine over heats? Of course not. The EPVS did more harm than good … not advised making it functional. Replacement coolant tubes have no provision for it either.
The OEM Pantera air cleaner snorkel had a long pleated tube that extended downward to a plastic end piece that scooped air from below the car … make that air, dust, rocks, leaves, candy bar wrappers, debris, etc. Great for sweeping parking lots. It was about as good of an idea as the EPVS.
Ford's normal 4 book workshop manual set was expanded to 6 books in 1973 … there was one whole new book for emissions equipment.