Welcome to TFF, Crocodile. There is no such list of serial numbers for pre-ban SKS's. The date of import is the important date, not the date of manufacture. And since Chinese SKS manufacture dates back to 1956, the imports are a jumble of all different types of serial numbers and dates. It would be possible to have a pre-ban 1989 model but a post-ban 1956 model. Unless they gave a list of every single serial number that was imported before November 1990, then the list would be worthless. A serial number range wouldn't help at all.
Sounds like you did very well on your purchase. So what do you have? What's the factory code? Pinned or threaded barrel? Stamped or milled trigger group? Blade or spike bayo?
I'm glad to see another person who loves the SKS and appreciates it in its original configuration. I'm an SKS collector myself.