Ultimately, it is all about too many sku's "on the shelves." Since Mopar had three lines Chrylser, Plymouth, Dodge which shared similar platforms, it didn't make sense to have separate models which were essentially the same car. GM did the same thing...
If you mean Plymouth, Devon, then Plymouth doesn't actually have it's own beach (like Blackpool, Brighton etc). The best thing it has is the recently refurbished Tinside Pool, which is on the Hoe. There ARE beaches around the Plymouth area, however, ...
plymouth was a division of chrysler . Most plymouth and dodge product were the same. I have a1999 plymouth neon. same as dodge neon. The parts are all interchangeable