GM wouldn't even use the Muncie 3-speed until '70. They bought Top loader 3-speeds from Dearborn until they cost too much. Those HD 3-speeds were miles better than the Muncie. I'm not suprised you "never heard any of this ****". I grew up street racing for beer money in the '70s. I put in my time and money on those Muncie 4-speeds, and IMO they are weak. That is not narrow minded, it is the truth. I moved on... just like I am about to do with this "conversation".
Also...I seem to remember Jenkins got his *** handed to him at the Nationals in that very A/S car by Stahls street Hemi.