I´m having an 8,5" axle in my '68 Camaro. The only thing we did was to move the mounts on the banjo. I kept the axle as it was.
I think it´s fair to say that not many would easily spot that I have a wider axle. I think the difference is 1" or so.
Keep in mind to have absolut equal angles on both mounts and watch the pinion angle.