Question about replacing 15x7 wheels with 15x8

Sorry, about the car mix up the OP has the Dart.

Anyway, if I had less back spacing I could have gotten a wider tire under the car but with the 4.5" back spacing it would be to close to the spring for comfort. A friend of mine has 275/60-15's on 15x7's on the back of his 67 Cuda. It certainly fills the wheel well more but IMHO it is starting to get the cartoon car look. I am quite happy with the 255/60's.

Here is a side shot of my car. The car still has the 225/60-15's on the front in this shot.