the 58 hood is a different curve down the sides to fit different shaped fenders [wider dual headlights] - the hinges are different, mounting to both the firewall and the inner fender and the hinge springs attach to a bracket on the inner fenders ... just won't work unless you put the whole 58 doghouse on .... and then the mount holes on the firewall would need some fudging and you'd find the 57 frame was too short to install the lower splash pan
simplier answer - I measured for ya, the 55-7 hoods are 41.5" across the front, the 58/9 is 37.5"
Bill
