Over this past weekend I got some goodies installed with one being an aluminum driveshaft (http://www.lethalperformance.com/05-...0d87184754e2c8). First off I didn't pay that amound for the DS, I picked it up secondhand from a FORD dealership for $350. A S197 GT was trading into this dealership with the DS installed so the dealer replaced with a factory 2-piece so then they could put the factory drivetrain warranty back with the car. I did a test drive last night and notice the car left lighter. When slowly releasing the clutch the car would grip and idle forward much easier. I drove the car to work today and it is a big difference. I would compare it to an CAI/Tune install...My factory two-piece shaft with all hardware weighed in at 44lbs. This aluminum shaft tipped my scale at 19lbs including the pinion adapter.
Only thing left is to get the pinion angle perfect (taking to a shop) and adjust my panhard bar. Also looking into LCA relocation brackets now and I should be set with the rear suspension.
Next I'm planning to jump to the front and install UPR K-Member with A-Arms...
**CLIFF NOTES** - I highly suggest an aluminum driveshaft (or carbon-fiber) to cut weight from the stock 2 piece. Supporting mods like adjustable upper control arm are neccessary.