Rear tire width max for 67 Barracuda

For my 2 cents worth rears should be fine. I run 275/60/15 with 8 inch rims 4.5 backspace and they fit perfectly inside the wheel lip with no rub. But I do also have inset leaf springs using the Dr Diff kit which moves them in I think from vague memory 1/2". 275 rears sure do look good on our cars.