Quote:

Fuel Inject it. That way you can use lean cruise.





A fresh rebuilt 318 Magnum MPI + A500 would seem like the most economical choice overall. Especially if you are including all the added costs of new parts.
The 318 Magnum already has:
Small high velocity/low friction hyd roller cam
fast burn, efficient combustion chamber
light pistons
Long ram intake
low drag 1.5mm piston rings
Very good Low RPM torque

Lean cruise it at around 16-17:1 A/F. I think 25-28mpg highway could be expected. You might get even better if can play with the PCM ignition timing via a SCT flash or the like.

1972 Swinger 3.6L Pentastar
Diablo CMR tuner