ISIS Underdrive pulley install help

[series20]

I have a 92 240sx and bought the ISIS underdrive pulley and was trying to install it but the proble, im having is the belts...Ive been to 4 autozones, 5 straus, 2 pepboys...I managed to get 2 out of 3 belts by comparing sizes but no one has the one for the power steering/water pump pulleys..it uses a 3 rib belt..what siz do I get? what brand? part number? lenth? anything would help.

[Matej]

The ISIS pulley is a knockoff of the Unorthodox one. Unorthodox has a pdf on their website with the recommended Gates belt numbers. Gates belts are sold by NAPA, CarQuest, and other places I am sure.

Alternator - K040285
Waterpump & P.S. - K030384
A.C. - K040345

[series20]

your the best dude, thanks

[Black240Ct]

those numbers didnt match up for me.. heres what i found

s13 sr20

Napa belt #'s

ps: 040330

alt/h20/crank: 050355