15x7 cragars on the front of a 69 dart?

I've got 15x8 with 4'' backspace on there right now with 215/60/15's off of another car just to set it down they "fit" under there but you cant take a turn hard or dip on a turn, they are definitely too tight,............................................................................. the way I measure 15x7 with 4.5 backspace would be perfect, just barely clearing the upper ball joint and outer control arm and putting it in as far as possible, I know 4 3/8 (the most backspace cragar will put on a 15x7) is only 1/8" difference.........................................................................I'm just hoping someone else has a similar setup because I really want the 7'' wheels and don't want to get 6'' just to play it safe. please chime in anyone with 15x7+ on a 67-69 dart with 73+ discs??????????????????????