71 Dart Swinger rear tire fitment

i wont get the car til this week but i did find out it is 4.0 sbp and wheel vintiques does carry a 15x8 rally wheel but im not sure on the backspacing.. i know tuckinauster said he has 5" backspacing.. Buschi340, do you know the backspacing on yours? and did either of you guys have to do any alterations? thanx for the info guys!!!!!