tire width

I am tossed as to whether I need to buy a leaf relocation kit. With the right backspace I am sure I can get a 235/60/15 drag radial in my car and with a leaf relocation kit a 255/60/15 drag radial. I do not think a 71 scamp wheel well will handle a 275/60/15 tire. I have ss leafs and will be adding a pinion snubber and at a later date slide link or cal tracs. 4.10's will be going in rear.
My 408 I am expecting close to 500 ft/lbs torque and will add a 100 shot of nos. The million dollar question is will a 235/60/15 drag radial tire handle this and would going to a 255 make much of a difference aprox. 1/2" extra width. I do not want slicks but also do not want to be always spinning my tires.Opinions appreciated.