My favorite Plymouth would have been a '64 Valiant S/S car that came with a Stage III Wedge/727/8.75" powertrain, with an aluminum front cap, and mini tubs.
But Ma was all about B Bodies, and the new Hemi, and never built it....
I think this combo might have kicked the Hemi's ***... Maybe they thought so too... and, that's why we never saw one.