I haven't seen a turbo kit for LT1 cars yet... I heard someone is working on one though....
for superchargers: This is an excellent mod, pretty easy to install, considering the power gain, and your car will still be reliable.
The best one to get is ATI's procharger (
www.procharger.com) they are intercooled, well built, don't require an oil line from the oil pan, and add 60-65% power on the LT1... you will be looking at a solid 450 HP if setup properly.
The next is Vortech, they are not quite as good, but still well built. On vettes they usually don't have an intercooler, which makes them cheaper, but also makes your safe max boost 6 PSI, instead of 8 PSI for the ATI.
The other superchargers out there are usually cheaper, but like anything, you get what you pay for. I would go for procharger, then Vortech if I couldn't afford the procharger.