Wirenut
I think AutoPower makes roll bars for Corvettes, and maybe Alston too. I think AutoPower will tell you how to measure and they will build one to your specs.
A standard unit will most likely NOT clear the convertible irons on the side and will require a special build. That would allow you to have a roll bar and the top still work. However, I don't believe that a roll bar made like that will pass inspection for racing because the hoop would not be wide enough to give really great protection for your head.
I'm going to have one built for my daughter's 72 LT-1 convert when I restore it this coming summer. I've had a complete roll cage built by a shop on Gasoline Alley in Indianapolis a couple of years ago and will probably have them do the roll bar.
Perhaps you have some race shops near you that you could consult with. If you are racing, read the rules carefully because they are pretty specific about what will pass inspection.
Good luck
Ol Blue