He told me that buying a used gear would be a bad idea because he wouldn't be able to set the contact pattern "perfectly"

A new ring and pinion from KIA is about 300-350 bucks IIRC. You can probably get one from a local KIA dealer\parts department. The 4.77s are found in the FRONT diff on the 4wd sportages.

 

Check mfactory's website. They still have 4.57s listed. Might be worth a shot to contact them to see if they have them or not

 

I made a comparison chart to help me decided on which gear to get. I know the 4.56 is no longer made but I know that the 4.44 is very similar to the 4.56.

 

I am running the kia sportage 4.77 gears in my ap1. ( this is out of the 4wd model) I have 4 track days on em so far and no issues. Must have upgrade for the s2k as ap1 gears are wayyyyyy too tall. Best par t is that the kia final drive cost $260

 

Yeah i heard its a definite must for ap1. I was planning on picking up the KIA final drive also. But im stuck between 4.77 and 4.44. Does anyone know the difference between partnumber mm05727110 and 0k01427110 from kiaparts.com. It only says its a final gear but it doesnt mention if its 4.77 or different one (4.44?)?