95+% of all SKSs in the US were imported AFTER the 1989 Import ban. So, yes, there certainly were a small number of rifles imported before the ban, and these rifles can be configured almost any way you like (except for NFA configurations). But the chances that you have one of these rifles is very small.
And, the problem is: you have to be able to PROVE that your rifle was IMPORTED before the ban. Without the original purchase paperwork dated before 1989, that would be virtually impossible. Some of the importers have gone out of business, and none of them respond to information requests of this kind from anyone but BATF. There are no serial number lists, and sequence means nothing, as these were surplus rifles in various condition made in various factories at various times.
So, unless you personally bought the thing before 1989, you should consider it post-89, and subject to the Import ban.
-Troy