Murkrow's a Gen II pokemon, and you don't need the National Dex for it like you did in GSC days, there are now two options:
1.Pokewalker - simply collect 500 Watts to unlock the route containing Murkrow, walk far enough for it to be available, then capture it before you run out of watts.
2. Like Slugma and Houndour, Murkrow is now available in the Safari Zone! Obviously, you need to go to the right areas (either pure luck, or wait a few hours after passing the first test, until you can do the second one, where you get to change the areas around).
nb. If you want Slugma, you can get an egg from Primo in Violet City Pokemon Center, although you need some special words. Houndour, sadly, is either Safari Zone or Kanto, no easy shortcut.