Demon Of A Tire Dilema

I'm Putting New Tires And Wheels On My 71 Demon. I'm Worried About The Fit On The Rear Tires I've Already Ordered. Does Anyone Know If A 255/70/15 Bf Goodrich Ta On A 15x7" Rim With A 4" Bs Will Fit Ok? The Tire Diameter Listed Is 29.1". I'm Worried Most About The Tire Diameter Being Too Large To Fit. Thanks In Advance.