Stop in for a cup of coffee

The only ref I recall seeing is the about vapor saver which had 4 tubes on the tank?
Heated Air Intake and "Vapor Saver" (Session 271) from the Master Technician's Service Conference

I'm use you can find more info. poking around the net, or maybe inthe owners manual.

There's a mention of a change in fuel fillers here, but I have no idea if that relates.
The 1970 Hamtramck Registry "1971 Dodge TSBs Index" Page