[JoeC]

Lakewood still sells the long bar and the short bar for 69 Camaro. They just warn not to use the short bar for mono leaf.
In many of the original pics (1967-1970) the Motion cars and Yenkos used the short bars.
This may have been for better ground clearance as there were still a lot of dirt roads and drive ways back then where the long bars would bottom.
The slapper bars that hit the springs are not a great design either short or long. Most broken leaf springs I have seen brake at the front eye where the long bar hits and the short bar looks like it will arc the spring.
But I have seen old school cars with long bars and short bars that still have their original springs. I have an old set of Long bars where one is mangled from a high speed bottom out.