Biggest rear tire in a 68 Dart?

To use the entire wheel well you will need to move the springs with the offset hangers. If not you will hit the leaf springs. The measure ments I took looks like I can go no bigger then 27" tall and 10.5" wide (section width not tread width) using a 15X8" rim with 5" of backspacing. Thats about the size of a 255-60-15.