I'm reading an interesting book right now that talks about neurological development that starts as babies. There is evidence that the types of behavior you're describing is due to neurological pathways developed as a baby. A common cause is TV watching at too young of an age (under 3) , which will disrupt sensory integration and attention span development, which are both developing at an almost incomprehensible rate at that age. Anyway, there are brain type exercises (therapy) that help build new neural pathways and integrate the different parts of the brain. I know there are therapists that specialize in this, but don't know exactly how to find them. There are books that will help, too. The book I have is for children 3 and under (Bright From the Start, by Jill Stamm), so you'd want to look for something for the older kids. If you browse Amazon, perhaps you'll find something. They are simple exercises, don't worry! Little games, etc.
And, this sounds strange, but you may want to try music lessons. Playing instruments is VERY good for integrating different parts of the brain. I hear drumming is amazing. Drummers do these complicated warm ups to get ready to play, because they have to be able to do different rhythms and actions with the different hands, while paying attention to what else is going on. There are community music centers for this.
Another thing you may want to look at is how he is sleeping. If he is not getting deep sleep for long enough periods, it will also cause this behavior. I have a friend who had her sons adenoids and tonsils removed, because they were too large for him to get restful sleep. She said it made a profound difference. She knew he was a bit of a light sleeper at night, but she thought since he was a heavy napper, it made up for it. But those are just signs of never really getting the right sleep. Children manifest poor sleep differently than adults, but as mamas we know how bad it feels to be chronically sleep deprived!