The Ford Barn - Rear bumper clearance

I am continuing the process of re-assembling my 31 Roadster. Right now I am fitting new repro back fenders. My rear bumper brackets appear to have been bent at one time and now the bumpers hit the "tail" of the rear fenders. In looking at the brackets it appears that both the brackets and the cross brace are bent. One bracket is bent more than the other as is one end of the cross brace . My plan is to straighten everything but it would be nice to know what the distance should be from the outer tip of the bumper bars to the tail of the rear fender. Any input would be appreciated.