Not trying to talk you out of a K, just advising that S&W has no replacement barrels for a 19, and with repeated use of magnum loads forcing cones have been known to crack.
Such things as firing pins & hammers are becoming problematical at S&W.
There are still many replacement parts floating around at gunsmith shops, but those will be drying up since S&W isn't producing any new ones for the older models.
I have several older Smiths, bought a new snub 66 last year. I'm not knocking them, just pointing out a potential situation with the out-of-production guns.
Get one in the best shape you can possibly afford & find, that'll give you your best chances of a longer useful service life.
If you get a 19, avoid shooting 125-grain .357 Mag loads through it.