Watch the Southern Jam - Rhythm online guitar lesson by TrueFire from Play Rock Guitar 4: Rhythm Principles
Southern Jam - Rhythm - Extended Performance is a video guitar lesson presented by Jeff Scheetz and is sourced from Rock Solid.
When it comes to variations of the southern rock chordal riffs there are plenty. We can really look at it two ways - one is that you are using other partial chord shapes, and the other is that you are using notes from a scale (usually pentatonic) to get your riffs going.
These variations will show you how to take a simple chord progression and make it sound a bit more "geographical".