Honestly at this point buy an Arsenal. Yes they are expensive but for many good reasons.
1) All imported from military arsenals (SGL's from Izhmash in Russia the place where they first made the AK, SLR series from Kazanlak in Bulgaria who is still the official arsenal of the Bulgarian military).
2) Factory-spec receivers
3) All brand new parts not an American mixmaster of dubious quality
4) Hammer forged chrome lined machine gun grade barrels that will be able to shoot any type of ammo you buy
5) Excellent build quality
6) Holds its value so one can easily resell it if they don't like it
7) Arsenal milled receivers are hot-die forged making them more durable than the Cold War era and domestic American milled receivers
Now is not the time to cheap out. Not all AK's are the same. I'd rather bite the bullet and buy quality then regret it after Oct. 1st dealing with a lemon knowing I am stuck with it.
Also the cost to convert a standard Saiga to Arsenal specs would put it above the cost of an Arsenal that won't hold its value like an Arsenal would.