I have a 67 Dart. I need to narrow my stock A body width 8 3/4 a little. I am trying to decide if I should just go ahead and get a Dana 60 and do the work to it instead. At my current power level I am fine, 411hp-410tq, but I am thinking into the future, cause I am sure it will get a little meaner. At what point does the 8 3/4 start to fail? This is just a street car.