Whats the widest tire I can put on a Dodge 5 Spoke Heritage rim? Its for my R/T is it a 20x 8 or 20 x 9 rim?

Heritage are 20x8 http://www.challengertalk.com/forums/f79/yes-275-40-20s-fit-well-1-7-lowered-classic-70607/

W/regard to only the rim and the tire, a good rule of thumb is that the tread width of the tire should not exceed the rim width by more than 2".