I was talking to a guy that owns a 1989 Supra with a 1JZ. He was talking to me about maybe getting a lighter driveshaft. He said that they are about 11lbs lighter, and it would be like taking 200lbs off the car as the motor has less mass to rotate for the power to get to the wheels.

Is there anything like this out for a 240z? A lighter, stronger driveshaft then what is currently out there?

Can't help on the driveshaft but I did read an article about somebody putting a carbon fiber one on a blown 280 in a specialty Z mag. I wouldn't put a lot of faith in taking off 200 lbs however. True you have less rotating mass but rotating moments have something to do with the square of the radius of the shaft I dimly remember from when I got my ME degree. Z drive shafts aren't very much diameter. You still have to make the car masss move forward.