Blue steel,
10, 13, 15, 19 all are K frames (the 19 is the blue steel version of your 66)
Stainless steel
64, 65, 66, 67 all are K frames.
The 13, 19, 65, and 66 are all chambered in .357.
The 10, 15, 64, and 67 are all .38 Special only.
15, 19, and 67 have adjustable rear sights, the rest fixed.
The cheapest in stainless will likely be the 64's or a 65 in 4" barrel length. (former duty guns)

(EDIT) You can single action a bobbed hammer UNLESS it came spec equipped or was altered to run D/A/O. Many departments, agencies and/or companies required it. Any can be retrofit to run D/A S/A again if desired. Personally for a S/D car gun IMHO your better off D/A/O.