69 valiant backspacing

im asking again because last time i didnt get much of a resposne and im hearing different things on previous posts so here it goes. if any of you have a 69 valiant or dart. what backspacing did you use? i have 245/60r15 tires and im going to use 15x7 in rims but i need to know the backspacing. please share what you have...