On a Barracuda you can do 235's as far as width goes, they should clear. The fenders are wider than the Duster's or Dart's. The problem you'll have is the length of the wheel opening and the height of the tire. A 235/60/15 is 26.1" tall, so you'll probably have to trim back the front lower corner of the fender at the wheel opening.
Anything over 26" tall gets to be a real problem for height. Duster's are only mildly better than barracuda's in the length of the wheel opening, the front and rear corner is an issue. Even the 225/60/15's are tight, and they're only 25.7" tall. Look at the picture I posted, and take a look how close the tire is to the rear corner of the wheel opening. And that was why I had to push the fender to bumper brace out, to clear the front corner. Unless your ride up at 4x4 height, anything more than 26" tall is going to be a big task to get clearance for.
