I was looking into flywheels and clutches a while back. I wanted to run an Aluminium flywheel on my LS1. An explosion proof flywheel is a definite must in one of these cars as the flywheel runs pretty close to your legs. For my peace of mind i didn't want to run the stock iron flywheel.
The reduction in rotating mass of the Aluminium flywheel makes your motor rev much quicker but it can make it bog down a bit off the start. The Cobra is a light car so doesn't need as much flywheel mass to help get it going.
Most of the Aluminium flywheels for my motor were about 6.5Kg (14.3 pounds). I ended up buying a Yella Terra lightened billet steel flywheel that weighs about 7.2Kg (16 pounds). Yella Terra make a very nice range of explosion proof steel flywheels. Their flywheels are often sold in the US under different maufacturers names.
Here's their web page:
Yella Terra
For the clutch I think I be buying a SPEC clutch. They seem to have quite a good reputation with the LS1 crowd and have a number of different clutch combinations depending on what you are doing.
Here's their web page:
SPEC Clutch
Cheers