As a wise person told me (and he owns a blackish R/T model), when you buy an "upgraded" Dodge Charger or Chrysler 300, you're paying for the engine, while everything else is left stock.
This is one of the few cars like that. Only the Holden Commodore, Holden Caprice, Ford Falcon, Jaguar XF, and Maserati Ghibli are also like that.
The 300 and Ghibli both are the "luxury" versions of the Charger (all riding on the same platform as the aging Challenger), the XF is the "luxury" version of the Falcon (the latest gens both ride on the same platform as the PREVIOUS-gen Mustang), and the Caprice is the "luxury" version of the Commodore (both riding on the same platform as the PREVIOUS-gen Camaro). Regardless, they still compete in the same E-segment family sedan body style category.
With cars like the Cadillac CT5-V Blackwing, BMW M5, Mercedes E63 AMG, Audi RS6 and RS7 however, you need to change most of the design to fit the engine inside. Those are full-fat sports sedans however, not really muscle cars.
The Maserati Quattroporte Trofeo and Porsche Panamera (of the GTS/Turbo S varieties) are in-betweener exotic sedans, all being both E- and F-segment. Those two adapt the sporty enhancements of the M8/Alpina B8 and GT63 AMG, while leaving only the size and comfort of the Alpina B7/M760Li and S63/S65 AMG.