Chris--
Please, I didn't mean to sound like I was taking you to task--it's just that there's a world of difference when it comes to fitting a holster properly to a gun, between the various gun frame sizes. Some, like your K-frame, the Ruger Security Six family, & the Taurus line, will generally, though not exactly, interchange--but it will be "close enough for government work."
The true large-frame guns (Smith's L & N frames) won't fit the same holsters. A K-frame would fall out of an N-frame holster, while an N won't even go into a K.
Just trying to help you get what you need!
David