Plymouth Feather Duster Questions

Feather Duster/6

Dodge Dart Lite /6

Check the carb, 1 bbl Holley that has a very different shaped booster than the std 1 bbl, people have claimed help get 30 mpg

Also check the exhaust manifold
Outlet, I believe it is larger diameter
Than std

EDIT

Aluminum:
Intake
Hood
Decklid
Bumpers mounts
Bored .030 over
Special cam