MOPAR's are set up for ported vacuum advance. That's what I would use. As you know, that will help mileage. Tires can help also. Not too wide, moderate tread pattern and max pressure. I don't know that carb, but if its black around the pipes agree its rich and needs fixed. How do the plugs look?

I bet she can do at least 2-3 MPG better with some attention.