I've got a .223 AK. There is only one true mag, but it works fine. Oh, and converted 5.45 Bakelites work too, but cost about the same as Weigars, after conversion.
Which caliber? Are you a "big & slow" person, or a "small & fast" person?
I'd want a 5.45, before a 7.62. The Soviets musta had some reason to make the change. And I think it would be more fun to shoot than a "bottlenecked .30-30."
If you're worried about ammo availability, get some dies and a reloading setup.
Hmmmm, wait a minute, does anyone make 5.45 brass and bullets?