Cadillac DTS alternator upgrade question

[ONLYUSEmeBLADE]

Hi there

2008 Cadillac DTS. Bought a mechanic alternator and I’m haveing mechanic come out to install the alt and also new radiator. Kind of a pain in the ass job. 

NOTE: This unit comes equipped with a smaller 1.75 inch
diameter alternator pulley. and will require a slightly shorter
drive belt for proper belt tension.

 

anybody happen to know which one to buy instead of buying several via the trial and error route?  Thanks in advance 

[Dafaseles]

Measure your old pully diameter, then minus the difference off the new pulley, and then subtract that off the the new belt. That usually works for me.