1970 Dodge Dart Swinger questions.

I am in process of getting a 70 Swinger and need help with tire sizes. Will be getting small bolt rallyes all the way around and want decent size tires but want no rubbing issues. Will be running BFG T/As. What size can I use to make the tires a little bigger in the back than the front? Any leads on a split bench seat with a fold down armrest in white. Thanks for the help!!
Chas.
P.S. Will 14X7 Western Indy Slot mags fit in the back or are these wheels too wide? They are about 3 1/4 inch offset? Thanks again.