U/D Pulley interchangability question 2001's..

I have an 01 GT, and a buddy with an 01 GT(still need to varify his build date), but while im waiting i figured ide just ask here..

He has a few bolt ons, hes going to give me for my stock pieces before he trades it in. (steeda) pulleys, (C&L)maf, intake, (dont know brand) t/b

What im looking for is dates when the change took place, as far as the underdrive pulleys are concerned. For steeda pulleys i see listed.. They have a set for the 96-01 (early production) and a set for the 01-04 (late production)

BTW, besides when the change took place, what changed as far as the pulleys or balancer are concerned?

why do you say this? did you have problems with yours, or have just heard bad things about them?
I know the guy personally, he has no use in giving me somthing that would cause problems.. Ive heard the guys car start up and run just fine( as good as mine, in stock form) and havent heard him complain about anything as far as the bolt ons go. So i know for sure, it works fine on his car, and his is an 01 just like mine.

Just wondering if you speak from personal experience.