You may have issues with the 8" wide wheels on a Dart. I also have 7"s with 255-60/15's And they are a tight fit on the quarter panel side. A finger's width of clearance on the spring side and not even my pinkie on the quarter panel side. And that's with the back up quite a ways. @sbmopar318
I've always loved the stance your car has. That picture of your car is the one I found a few years ago when I was searching images to find the right tire/wheel combo for my Scamp.