From your own link...
1968 Plymouth Road Runner vs. 1968 Dodge Charger
May 2, 2014
CRO Exclusive
Although both the 1968 Road Runner and the 1968 Charger R/T were built on Chrysler’s B platform, there were distinct differences between these popular muscle cars.
https://www.coolridesonline.net/news-blog/1968-plymouth-road-runner-vs-1968-dodge-charger/
Yeah, I get that but you’re totally missing the point. The chassis and body are the same period. You’re quibbling over cosmetics or performance packages. Bottom line they are the same cars. Take a Charger door off and it bolts right up to a Roadrunner. Do you get my point yet? You seem like you’re arguing for the sake of trying to prove me wrong and you’re not winning at that even.