The 1990 import restrictions have nothing whatsoever to do with the 1994 AWB and remain in effect. Pre-1990 AK clones have pistol grips and often have folding stocks. Post-1990 AK clones (MAK-90) have thumbhole grips, since pistol-grip semi-autos that feed from detachable magazines are not "sporting" firearms.
The distinction between pre-1990 and post-1990 firearms remains significant, because BATF regulations forbid anyone from modifying firearms imported after 1990 into non-sporting configurations.
My question, in simplest form, would be "is there any problem with importing a barrel nominally intended for use on a "sporting" firearm (a MAK-90) for the purpose of using it on a "non-sporting" firearm (a pre-1990 semi-auto AK)?"
The only legitimate solution is to do away with the distinction, H.R. 1703 does that!
Since there's no way for the BATFE to know if the incoming parts are for rifle imported before or after 1989, this current ruling probably bans them all -- though logically it shouldn't. I admit that logic doesn't mean a thing to the bureau that made this ruling.
I'd say your best and cheapest bet is to get a 'Pre-ban' barrel for dirt cheap and modify it to fit your pre-1990 rifle that allows 'evil' parts. Those with a 'Post-ban' should adopt ten parts and ignore the situation altogether.
Hell, best idea of all is take your expert legal defense team with you to and from the range.
To answer your question, you could use a foreign barrel if it was imported prior to Sept. 10, otherwise, it has to be a US manufactured barrel (if you can find one).