gbopp,
The 1958 Chevy Impala Super Sport was available in 2 versions. The 2 door hardtop and the convertible and both had the Continental spare tire mounted vertically inside the rear bumper bulge out. Mine was bright red with a white light cream colored roof and was a real boat in length but what a sweet smooth riding car. Didn't have the fender skirts and still don't like the looks of that option. I remember it as having the 438 big block engine with the turbo-thrust 4 barrel but that was 46 years ago and gas was a whopping 25-28 cents a gallon. 11-17 cents a gallon during the frequent local gas wars.
I loved that car so much and wish I'd kept it and could have afforded to just store it as it's would be worth a mint+ today. For some of us, getting a good education ranked way above a car that could be replaced anytime and you do what you have to. The guy who'd bought it from me moved away a couple months later and I've never seen it since.
I agree that the 1958 and the 1957 decked out Chevy's were the coolest and most beautiful cars ever built. The 1958 gullwing design never gets or got old!