That article is nice, but it does not provide the revisions post the 29-6:

29-7: change to MIM trigger/hammer and move firing pin from hammer to frame mounted (1998)
29-8: new frame design with internal lock (2001)
29-9 and 29-10: cosmetic changes only

It's my understanding that you want the 29-5 or 29-6 if you shoot alot, as they incorporate all the good design changes to the yoke and internals, but dont have the frame mounted firing pin and MIM internals or the silly internal lock that so many of us despise. If looking for a 629, the 629-3 and 629-4 were the equivalents in stainless.