[Hersbird]

The special edition mid 70's Feather Duster supposedly got in the 30's stock with the 4 speed manual and slant 6 motor. They had some light weight parts and a lean burn tune on the small carb. Too bad most came with the non-overdrive automatic option and then got hacked up turned into drag cars with their lightweight partts.

From allpar.com
"The Feather Duster included aluminum replacements for the inner hood, trunk bracing, bumper brackets, and intake manifold, cutting weight by 180 lb (around 5%). It had a smaller single barrel carburetor, economy distributor calibration, large exhaust, and a 2.8:1 rear axle ratio, with a choice of three-speed automatic or four-speed overdrive manual transmission.

While acceleration was compromised, the Feather Duster was now rated at 22 mpg city, 31 highway with the automatic (a stunning 24 city, 36 highway with the manual), and was larger inside than many other economy cars, though acceleration took a hit. The Feather Duster was a fine alternative to the extra-slow Japanese imports that customers were waiting to buy, at list price; or at least it would have been, had more people considered it over the quick-rusting Coronas, Civics, and Datsuns of the time."