You can go further into the tinkering if you look around in that some places are selling the original gas blocks with bayonet lugs and original front sights to take a cleaning rod also... as the SA85m with dumbholes have the notch cut off to hold the rod.
This was a thumbhole that I converted around 2000. I had no trouble finding the nice original stock and pistol grip. You'll need a pistol grip screw and wedge nut and you'll probably need to fit any butt stock you get but its pretty easy to do. The problem is a stock like mine is going to be hard to get these days.
Russian spec. AKM furniture may need a little sanding / filing / shimming to work (for example, the butstock might need to be filed and the front handguard retainer might be a little different specs) but once installed its a great upgrade.