70 dart 14" rallye rim widening

Well I found a local place to widen my wheels. They're charging $125 to add a 3" band to two wheels and I'm getting 245-60-14 TA radials. I'll post pics when I can. It'll be about a week though...Dean
So keeping the backspace the same and adding 2 1/2 " to the offset side is Ok for a 1972 duster with stock 8 3/4rear end with no tire rubbing? 14" rims.And has anyone used greens in richmond for this on their mopars ralley rims?