paxton pulley?

try ebay.

Also that blower is not recomended to exceed a certain amount of rpms.

Which if I remeber correctly with an 8 lb pulley is roughtly 5500 rpm so if you upgrade the pulley it would mean that you couldn't rev the motor up before doing some damage to the blower.

Also recomend getting an oil cooler for it. Change the fluid at least every 1000 miles.
 
While I don't remember the exact numbers I had calculated, the 1200 can have a max impeller rpm of about 40-50,000 rpm. There is a calculation to figure out that speed based upon pulley diamters and engine rpm, I'll see if I can find it. The 5500 rpm rating for 8psi is based upon a bone stock 289 which is it's effective usefull rpm. Although I have not used mine yet, I would suspect reving higher than 5500 will yield greater boost. Keep in mind more boost means more heat so an intercooler becomes necesary to keep from retarding the timing too much.