John,
If you turbocharge your SC, then you may be able to keep the SS headers. You'll run the turbo pipes after the headers. It's easy to keep 1 header. It might need a lot more work if you'll keep both headers. You may still either keep the NOS or ditch it to make it more simpler in the fuel/timing setup. Or if you decide to go for a centrifugal supercharger, you'll keep your custom exhaust system. You'll have better performance than those with only the supercharger setup.
I know a stock turbo SC can't keep up with the 911 on curved roads, but there've been sereval Japanese SCs that run with all kinds of other cars at the professional tracks. I believe they're heavily customed in weight and suspension systems. Regards to handling, I still missed 1 of my Hondas. It handled around curves like a hot knife cutting butter. It's smooth, quick, balance, and crisp. It gave me the feeling of the roads. I drove around the entrance and existing freeway ramps at 60-70 mph with no problems.