I'd adjust the valves, and I think those years were jetted lean. You might want to try jetting richer a step at a time. Your electronic ignition will work great, nothing better. Check to be sure your vacuum advance is working. Play with timing, trial and error, and see if you can't get better power and mileage. Also get a vacuum gage and cruise at the highest vacuum for your given speed. We used to go 300 miles per stop V8 or /6. You should be able to get 20 mpg. I used to work at Chrysler up to the mid 70's. I loved those A body cars.