The best quality in a 'classic' (non-Monte Carlo) sporter-type stock for the SKS I know of is in the Choate and Butler Creek brands. Even with those, be aware that there may be fit issues due to the relatively wide tolerance spreads among the many different countries of manufacture and even within different examples of the same origin.
The Choate comes with a spacer piece for placement at the rear of the receiver if necessary. As neither of the above have the cross pin of the military stocks, some models or examples may be a loose enough fit in the aftermarket unit to move slightly under recoil, as there must be a certain amount of leeway for the action to pivot when installing or removing the stock due to the way it's designed. The cross pin arrangement mitigates this quite a bit in the original stock, as well as reinforcing the rather thin and fragile wooden fore end against splitting.
I tried the excellent Choate on my favorite Chinese commercial SKS for a while, mostly to get the longer LOP. It fit fairly well, but even with the spacer in place a good deal of the residual movement during firing was being absorbed by the tip end of the forearm where it mates with metal retainer piece. I never could get the same level of consistency in my groups with it as the with the wooden military stock, and they averaged a bit larger, too. YMMV, as I ended up trying it on my Tula-made Russian 'shooter' where it works just fine.
The cheap fix is the thick rubber butt pad. It adds an inch to the LOP, install right over the existing item, and allows you to keep the cleaning kit in the butt trap. I put one on my Chinese when the Choate didn't work out, and it does make it fit me better and handle more comfortably. Not very aestheticly pleasing, perhaps, but highly functional.
I suppose that one could 'glass bed his SKS into one of the wooden or synthetic aftermarket units to get a precise fit, but it'd be tricky, IMO, and likely not yield enough in the way of improved functional performance to be worth the trouble and expense.
. what do you think about this stock? 
