So after surfin around on Summits website I came across a 3 piece bbk under drive pulley kit. Its listed for a 2002 5.4, my truck is a 6.8. But being the two different motors take the same belt, tensioner, idler pulley, and power steering pulley it should work on my 6.8.

So good or bad for the motor? I've red some stuff both ways, not sure if its worth it or not.

 

I wouldn't. I'll make your lights go dim when you put the truck in drive at night.

The alternator has to be spinning a minimum rpm to output enough electricity to keep up with your accessories. Underdrive pulleys screw it up. Besides, if the accessories didn't need to spin the speed they spin, don't you think that Ford would have made them spin slower? Just my $.02