The Southern rock bands of the 70's were pretty big underground competitors to most other mainstream rock at the time. Our surf crew was into them quite a bit, compared to most arena/big hair/glam rock bands getting majority attention at the time. Lots of true gems can be dug out of most of them. Many are forgotten or not so PC anymore, but that was then.
Here's an interesting cover that is pretty damn cool.....
Aussie redneck headbangers.
You can add Lynyrd Skynyrd, Allman Bro's, Charlie Daniels and a bunch more, but these above are less known/played.