For a while guys on the drag racing side have been working out how to drop weight on the Challengers and getting 400-500lbs off is doable (costly if doing it after the fact but certainly quite achievable if starting from scratch). The lowest weight Chargers/Challengers in the drag race circuit are currently around 3200 lbs.
As someone pointed out, the 426 aluminum crate motor is available and can easily be dropped in. So a 3800 lbs 426-powered Challenger making about 550 crank hp N/A is very doable. Some changes to the body (e.g., a wide-body kit) and it can also accommodate more meaty rear tires. Can it compete in the handling department? That would remain to be seen, as the Challenger is a bit more nose heavy than the Camaro.
2009 Dodge Challenger SRT8 6spd/BES 426 stroker/heads/cam; Pedders Justice suspension
575 rwhp on 93 octane/600 rwhp on MS109