The fender braces at the top of the cowl are different but I don't think they make a difference in locating the fenders. Just a different design. I think they changed in 58, but don't quote me on that!
55.2nd braces are sort of square with a curved head and are mounted/spot welded in three places on top of the cowl where as 59 braces are more of a round design and if memory serves me have more surface area attached/welded to the cowl.
