i would buy a 3.4, 3.2, and 3.0 pullies. with a cam and headers you should be able to start off with the 3.4 and get it dialed in without knocking. you might be able to run the 3.2, but the 3.0 might need a little more work (intercooler). having a 3.3 or 3.1 would be useless as the differences wouldnt be that much, but you can try those out too if youve got money laying around. i always just had 3.4, 3.2, and 3.0 pullies.