1971 Duster Handeling

Is there anything I can do and not add aftermarket exterior pieces?
Honestly, no. Not really. I mean maybe a chin spoiler, but even that would be aftermarket. These cars weren’t ever designed for that speed even if their speedometers claimed it. They were designed for a few quarter mile passes, sure. But not sustained on road speeds of that nature.

why the need for that speed on the road? Heck, the roads here can’t even support that kind of speed, too many pot holes