Widest Tire/Wheel combo for a '72 Duster?

hey 7172duster my 74 duster has the complete caltrac setup in stock local, question is everything in factory local with a 15-8 with 4.5 backspacing will a 27-11.50 hoosier qtp fit and not hit anything, what do you think, i saw the pics of your car and it looked like you had some pretty good sized tires under it