I'm pretty sure some early 70s Imperials came with some kind of anti-skid brakes.
The 1971 Imperial was the first American car to offer a four wheel anti-lock braking system.
http://www.imperialclub.com/Yr/1971/SureBrake/
Recently, I managed to locate a series of road tests done by the Michigan Department of Transportation using a '71 Imperial with the SureBrake system and a Buick with a two wheel (rear) ABS system. Look for it on the club website soon.