I'm interested to know how you picked those 4 to choose from! The Shelby is worth more than the rest of those combined, so gotta be the Mustang. Now if the Corvette was a 63' or 67'...nah still the Mustang.
1967 Shelby. That would be the rarest of the bunch.
And would increase in value the most.
Always look at;
Demand and popularity
Current market value
When buying a classic. I want mine to go up in value not
stay the same or go down.
The Audi S4 of course... You can't drive those cars everyday... they'll just become boring and oldish. You'll only know this if you've experienced it. Sure, they're fun to drive on Saturday afternoon and Sunday but imagine commuting to work 70 miles each way in a 65 Vette!!! First thing that you'd do is get much quieter mufflers. Basically, the Audi S4 is more practical. And yes, I had 5 muscle cars at one time so I know the deal. All you need is a water leak somewhere to wish you had a new car. haha