Improving MPG

To those 'advising' to just get a more modern pos...
There's another thing about properly tuning your engine... With a well tuned and set up engine you get a way more pleasant and fun driving car.
It's not always about the money 'spent'.

When I swapped the 904 in my Dart for an A518 OD tranny I got a much more fun car to drive in return. Which to me was worth far more than the cost of the tranny-swap.