Hi 3B...
I had a friend check a 1968 truck, and he pulled the rod. It seems to be the same size. I know what you mean regarding the brakes. This is why I am upgrading to a dual brake line setup. I lost my brakes on my other truck, and it was not a fun feeling.
It is funny.. so many people from my cruise nights told me it is a simple upgrade.. but now that I am having problems, those who told me it was simple are scratching their heads..
..Russ