that is fraud and with your evidence you should call your local states attorney and file a complaint.seriously.if you don't people will continue to get screwed by that dealer.
not everybody wants a 5.0.some have more fun modding a turbo.I have driven the 5.0 with auto and 3.15 gears and i was not impressed.if I was going to go V8 it would be a scat pack challenger but,im perfectly happy with my PP ecoboost.
test drove a GT recently with auto and the not so good gearing(3:15?).I was not impressed.my eco was not much slower feeling and with PP,handles better.