275/60/15 on rear of Duster/Dart

that is a big tire. what gears are you running and do you have enough torque to spin them?
The gear in it is a 2.94 Will there be enough torque, IDK, but fuel economy will be great!
That 27" tire along with the above gear ratio, at 65MPH, will only be turning 2377 RPM's

I could swing for a different gear, but this car is for sale as soon as it is completed, and if I keep changing things, it will never get completed. LOL