Several schools don't "fit" really.

You could argue A&M because Texas isn't truly the South but culturally A&M fits pretty well, we are the most Southern cultural part of Texas generally. We bring a lot to the table though with academics, money, and TV sets. Texas feels like much more of an SEC state now and it didn't 10 years ago.

Mizzou is awkward for the many reasons listed but they bring a lot to the table as mentioned. The demise of the Big 8 basically took away the home for the lost souls in the middle of the country that didn't really fit anywhere else with Colorado being the only one that wasn't in a really boring part of the country to live with little personality.

Kentucky honestly is just as awkward as Missouri, they have just been around a long time. Lexington is pretty damn far North and is closer to Cincinnati and Louisville than it is any major Southern State (Cincy and Louisville sure as hell aren't Southern). Kentucky has a lot of SEC history though, brings the basketball component, and has some Southern cultural feel.

Vandy feels like it should have left about the same time as Tulane, they made nice bookends but they are basically like Rice was to the SWC.

Texas and OU aren't SEC culturally at all. Austin and CS may be 90 miles apart but culturally they are night and day. OU loves football but it's definitely not the feel of an SEC school or state.

The most SEC like school that isn't in the SEC to me is easily Clemson. Everything about Clemson screams SEC.

Doesn't really matter though, all the conferences will be blowing up in the next few years anyway as we move to Super Conferences. Writing is on the wall.