Manowar- If you haven't heard much of their stuff you haven't heard much.

Judas Priest- They have around 300+ songs (I think), ideal stuff for a long road trip.
Dream Theater- Train of Thought, Systematic Chaos, are fairly thrashy. It's an awesome band for road trips. (42 minute long songs)
Thats just a few suggestions, hope they help/aren't too late.