Rear tire width max for 67 Barracuda

I have changed my Strategy....I'm going with : Wheel Vitiques 15x7" in. Fronts with 4 I/4" backspace+6 mm offset, 235/60/15" tires. Rear will be: 15x8in. 4 5/8" backspace+3mm offset..275/60/15" tires. Should be No Problems with spring clearance or fenders. What ya Think? SP. All replies welcome.