There shouldn't be any fender/tire clearance problems on Challengers, in particular, using the 17x9 rims with 275-40-17 tires... front AND rear... there should be plenty of room from the lips (front and rear) and rear leafs. At the most, only slight fender lip rolling would be required if you have a soft suspension. I wouldn't install the KYBs... they are weak and not considered much of a performance improvement.. there are many better shocks ... spend a little more and you get what you pay for with shocks. The back-spacing on the new YearOne rims is correct for both the 8" and 9".. so, the tire should be kept in the same centerline of the original factory rim location... only the tire gets spread out a little more, as well as the extra width of the tire. (I believe the E-body Cudas have very slightly less fender clearance... thus requiring the possibility of lip rolling just a little bit, but even the E-body Cudas shouldn't have any problem.)