I'm running 275/35/18's. The rims are 18x9" with +35mm of offset (6.4" backspace). The offset is misleading, I have dr diffs 13" rotor kit and that adds 5mm, and I run a 3mm spacer. So, if you're comparing to 73+ disks it's about a 27mm offset, or 6.1" of backspace.
That's for a Dart or Duster. Obviously the frame clearance is the same as a barracuda, but I think the barracuda fenders are a teeny bit wider because of the body based on some of the combo's I've seen. I don't have a barracuda though. But to run 275's up front you need about 6" of backspace on a 9" wide rim. Plus what're your brakes add compared to the 73+ disks.