The long-running question is what the H in group 3 represents. It would be easy to eliminate what it does not represent, if we had enough body tags and corresponding PHS packets.

It most likely represents a body piercing or welding, such as rear speaker, rear defroster, antenna, console, second trailing arm, hood tach, dual exhaust, etc. Certain items can be eliminated because they have other codes on the tag. The trick is to find one item that is consistent regardless of configuration and we now have 400s, 326s, Sprints, automatics, and manuals bearing the 3H code.

It used to be thought that 3H meant Sprint, but as soon as 3HF cars were documented it was clear that 3H could not mean Sprint, as there is no such thing as a Sprint 400.