Well, I hate to disagree with ya but there apparently were/are. Passon Performance sells specific bushings as well as a caged roller bearing for the clutch. Brewer's has the HD bushings AND roller bearing listed as well.. And here's a link from moparmuscle that discusses ALL of the 4 speed pedal assemblies and they even have a photo as well as mention the HD 67-up pedal version for the 340/383 bb cars.
It has larger diameter bushings, a caged roller bearing for the clutch pedal, a larger assist spring, and a tin shield around the larger assist spring.
