On the 2nd gen. 24 valve trucks, this kit is an improvement over the stock pickup which can eliminate noise and vibration coming from that area of the tank.
On the 3rd gen trucks, this kit upgrades the FASS fuel pickup location on trucks that have had a lift pump failure and had the in-tank module replaced with the in-tank lift pump. The fuel pickup is smaller on the '05 and up trucks due to the updated lift pump located in the tank. When the lift pump is replaced by the dealer and replaced with a new in-tank module with the lift pump located in the tank, the fuel pickup is also changed to the smaller '05 and up version.
Installation requires that you drill a hole in the top of the tank and install the pickup so that it doesn't interfere with the fuel float. Make sure the bottom of the pickup tube is close to the bottom of the tank (within the width of a finger) so that you don't starve the pump when the fuel level gets low.
The kit provides the parts to install a 1/2 inch pickup tube in the tank for the FASS System.

Resources:

Image(s):    Installed pickup tube