Your coworker may have that impression because he's dealt with stocks that weren't appropriate for the SKS at hand. If I recall correctly, for the Chinese Type 56 SKS, there are the blade bayonet stocks for long or short lug threaded barrels, and spike bayonet stocks with short lug or pressed/pinned barrels (and maybe a few early ones for long lug threaded barrels). Wood stocks for spike bayonet Chinese SKSs are generally relatively easy to find on the secondary market, eBay, GunBroker, and sometimes a few of the small "retailers", like sksman, etc.
Please post a picture of the barrel lug region of your 1978. I believe they were all pressed/pinned barrels by then so you'd want to get one that's for that style of barrel. When you're looking, ideally pictures of the inletted portion of the stock in the recoil lug region would be most helpful in selecting the correct stock. They still might require minor adjustments for fitting, but easier with wood than plastic/composite aftermarket stocks. I have no direct experience with plastic stocks but I've read a lot of posts on the subject where the word Dremel was used
You can probably read my bias, I'd go with wood