The biggest limiting factor for accuracy in an AK is going to be ammo.
Krebs custom used to do custom work on AKs. I'm not sure if they do any longer or just do packages. At one time they would install match barrels and do other touches to bolt and carrier to improve accuracy.
Also realize precision accuracy is not the strong suit of the AK. Also once you start making mating surfaces really tight you may sacrifice some if the wide tolerance for a wide variety of ammo. So, I'd try to figure out what you really want out if the gun as a priority.
How accurate do you want it to be? What kind if range and size if target are you wanting to hit? What ammo do you want to be able to use?