Besides superior strength the carbon fiber driveshaft doesn't fall in to vibrations which can happen with the metal ones.
But you get two aluminium ones for the price of one in carbon fiber. Just make up your mind on what you want...
(The upper one in steel looks bent - it's because of the camera lens)

New carbon fiber driveshaft is a little shorter because of the longer 4L80E transmission, it is almost of OEM length.
It is custom made at Precision Shaft Technologies In Clearwater, Florida.

For sale in 2009 since I no longer have any use for this back-up drive shaft. Pretty tired of bring it it to
every race together with the back-up transmission. Check >4SALE page

The 1350 slip yoke that comes on the Mark Williams is a little longer and have to be grinded for proper fit.

Mark Williams carbon fiber drive shaft. Since I'm going to change to the longer 4L80E transmission
I need a shorter drive shaft. I'm ordering one just like this but of PST brand. Made for high torque vs. high
weight. Another concern was the quite long Center-to-Center length of 55.11" (1400 mm) which an
Impala SS has with the rearend moved 3/4" backwards. Weight: 18,7 lb (8.5 kg) 1350 U-joints.
An expensive beauty, but cheaper than two in chrome moly...

When using a driveshaft with larger diameter like the Dynotech and Mark Williams TOGETHER with
a 2" lowering of the body like I have - it's recommended to increase the clearance in the rear part of
the driveshaft tunnel by raising it.

Spicer 1350 for the bigger U-joint, better than Chevy.