One of the last parts of my drive train that had not been replaced or otherwise rebuilt was the driveshaft.  The stock steel driveshaft isn't necessarily bad to have, but it was not meant for high performance use.  Especially after years and years of corrosion, and fatigue.  The rust and years of use can weaken a driveshaft to the point where it should really be replaced.  Especially if the car is driven at high speeds.  The faster a driveshaft spins, it gets more and more unstable at a square of it's speed.  In other words, if you spin it twice as fast, the stress it undergoes is actually four times as much.

The stock steel shaft in Thirdgens is 2.5" in diameter.  Some Thirdgens that were equipped with certain option packages came equipped with an aluminum driveshaft that measures 2.75" (as far as I know...).  The aluminum shaft is lighter than the stock steel shaft, and allows less rotating mass to create parasitic power loss between the flywheel and the pavement.  But, a larger steel shaft will provide much more strength than an aluminum shaft.

The driveshaft that I decided to go with has a steel 3" diameter tube, and reuses the stock yoke.  It was also built with heavy duty "Brute Force" U-Joints.  I had the shaft custom made at a local place that makes driveshafts, universal joints, etc.