If he's dropping his head and you have a lot of weight in the bridle, I would look at a Pee Wee bit. I have had the same problem with my OTSTB who was a horrible puller on the track (to the point he has a healed but a torn lip and a jaw that was bruised at the bar from his pulling so hard) and was miserable to try and ride as he would pull you out of the saddle. I borrowed a Pee Wee from a friend and he stopped pulling immediately (he was very angry about that) and now he is a much calmer horse who realizes the bit is something we use for communication and not as leverage.
I use the bit still as he also has a very fleshy tongue and low palette so most snaffles even French Links irritates the roof of his mouth. He is gaited and will single foot wonderfully with just light contact. He is still learning and is very green for him racing for 8 years (he wasn't driven much he was towed behind another horse because of his pulling so he has a tendency to "zone out" and is learning his brain and attention are needed) and I found this bit gives very clear signals and I'm able to use just the lightest of finger pressure to get him to move.
I seldom use the bit as a fix but sometimes if a horse has an issue I found that finding a bit that is more comfortable to the horse can solve a lot of problems, after that it's just wet saddle pads.