Make sure you have the proper Z-Bar..
Frequently the wrong one has been installed in our old Mopars now being > 40 years old...

In my 70 RR I had this issue of the clutch pedal not returning... And when replacing the clutch I took my Z-bar to our local Mopar guru. He proceeded to pull out (3) different Z-bars, all of the same width but with the tab fastening the adjusting pushrod in different positions. My 70 RR had the wrong Z-bar with the pushrod tab in an incorrect position.

The proper Z-bar is one that has the tab that postions the adjusting pushrod, so that it is parallel to the bell housing not angled.. This assures much better leverage and accurate return path..

Just my $0.02...