A magnet will help a lot.
* 1976 only option.
* Slant 6 only engine. It had an aluminum intake manifold.
* Underside hood bracing & underside trunk bracing were aluminum.
* Front & rear bumper reinforcements are aluminum. (It's contoured to fit inside the bumper and is bolted to the "shock absorber" style bumper brackets.)
* If it's a 4-speed, it will have an aluminum case and 4th gear is O.D.
The Dodge version was a Dart Lite based on the Dodge Dart Sport.
There may have been a point where they ran out of specific "Feather" parts. I went to buy a hood/trunk combo from a Feather Duster a while back. While the hood and trunk paint was OEM and matched, the trunk did not have the aluminum underside bracing. So I only bought the hood.