I saw my dentist today and she didn't even bother to take an x-ray after checking my mouth out. Apparently my symptoms are classic for clenching or grinding, and she thinks the whiplash altered my alignment just a bit - just enough to cause a problem. I've a significant overbite and she is actually surprised that it never occurred prior to my injury. Anyway, she recommends I try the inexpensive mouth-guard version from the store and if that causes a problem we will discuss a true custom hard version.
Apparently this can present with either muscular problems, dental pain, or both. In my case it is purely dental, I don't know if that is a blessing or not... Anyway, at least I now know what is going on, and that is a relief.