My friend has a 2000 lightning and wants to do the pully upgrade he would like to no the pro;s and cons, of this up grade. and he is looking for a company to buy them from. thanks in advance.

 

If you are talking about accessory underdrive pulleys, they don't exist for the Lightning at all. Now, if you are talking about supercharger overdrive pulleys to increase boost, you can get them from a number of various lightning tuners such as Motorhaven, PSP and others.
http://motorhaven.autoanything.com

I don't know of the other websites.

2002 True Blue SVT Lightning
-all stock and will stay stock