What do people mean when they say, "there is no factory support" for this model 66? If you purchase this older Model 66, you shouldn't expect any warranty support for the kind of damage on this handgun, if for no other reason than you would be the 2nd, 3rd, or only God knows how-many-eth owner of this 66. In addition, this damage looks to be because of misuse or some cause other than the original quality of the gun. Does the S&W Performance Center no longer do work (that you must pay for) on older S&Ws? It has been a few years since I've had any work done by them, but they worked on some S&W revolvers of mine that are much older than this M66! When I want the work done right on a S&W revolver, I've always depended on the S&W Performance Center. If nothing else, if you buy the gun, I'd have the Performance Center go through it completely and see what they think needs to be done to the revolver. You'd have to buy it first, of course, but it is a chance you may have to take.
I too have a love of 3-inch S&W revolvers. They have a full length ejector rod while the shorter barrel revolvers don't. Also, I think they look better and shoot better (maybe because I like them so much). You might want to look at getting a 686-plus (the 7-shot gun) with a 3" barrel. They are still available brand new. That is on my personal list of new S&Ws to buy.
Like others have said, I would have the firing pin bushing replaced before I depended upon this gun for self defense. The loaded cylinder might turn just fine with unfired or dummy cartridges, but I'd be EXTREMELY concerned that the primer of a full power/pressure .357 Magnum round might flow back into this notch and tie up the gun when you fire it! If this happens in a self defense situation, it might cost you your life!
Whelenshooter