I think this thread is getting a little fussy.

While Chrysler was not the decentralized company that GM was, there were some independence between Plymouth and Dodge. That's why one had the Barracuda, the other a Charger, etc. and, most famously, Plymouth had a Road Runner and Dodge began crying for a similar model.

I reckon when it came to the E-bodies, both companies' respective product development departments determined the available equipment and what was standard and what was optional. They also had base price points to meet, which could explain something like road lights being standard for 'Cuda (at least for '70) but gauges were optional, unlike the Challenger R/T (there's not many cars that had gauges standard, FWIW).

What I think is strange is why Dodge kept the 340 away from the R/T line, unlike the 'Cuda, but it may have to do with the idea that R/Ts had been synonymous with big-blocks up to that point; of course, in '71, the 340 was available for both the base Challenger and R/T.