I'd think 400 lbs is doable. Rip out sound deadening, hood and trunklid strengthening, extra structural supports, lighter suspension and steering compenents, etc. They did say this started out as a street car and not a body in white. Perhaps a BIW will be a future offering from Mopar Performance.
Found some more photos http://itsracingtime.com/new-blackfores ... /#more-171