Re: sks with tapco 20rnd mag
Yes...you can grind off an area on the bolt to enable mag removal with bolt closed. Longspring, a member I haven't seen on in a long time, posted some pictures and complete instructions for doing this. I don't have these instructions anymore but you might try to do a search for past posts by Longspring. He's pretty much an authority on the SKS.
As far as the mag not fitting in the mag well, if this has the original wooden stock it is often the case that the sides of the mag well have to be shaved a bit to fit the mags. If you install one of the after market poly stocks they are generally designed to accomodate the hi capacity mags.
Just a personal opinion here. I had an SKS that i tricked out with a tapco stock with collapsable butt, pistol grip, and hand guard. I then bought some tapco 20 rd mags as I thought loading with stripper clips was too tedious. I ended up selling the rifle to a good friend. It is an excellant shooter, however in retrospect I wouldn't make those changes to one again. I'd prefer to recognize the SKS for what it is; a very reliable and accurate piece of history. It will never be an assault rifle, so I would practice with the stripper clips until I got it down. If you still have the wooden stock, I'd reinstall the internal box magazine, and use clips. JMO