I was pleased that I was able to find just about every part required for a late emission system in my collection of stuff. Missing only the subject item below, the Temperature Controlled Vacuum Valve. I will keep it all together, hope I'll never need it.
I wonder about one thing. Above, George said "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".
Looking at your schematic above, it appears that the 'Temperature Controlled Vacuum Valve' presumably opens when the engine warms up, which then allows engine vacuum to control the EGR valve.
Is the EGR valve simply an open or closed device, or does it feather the valve depending on the strength of engine vacuum? In either case, since idling is a high vacuum situation wouldn't the EGR valve be open at idle when hot?
The rest of the plumbing seems to be primarily related to trying to control idle speed to control overheating and sensing intake air temperature to control the flapper in the snorkel.