Tremor was a trim package, just like the FX4, EDGE, or XLT.
My guess as to why you need tow hooks is to make sure you have the hole in the valence. Those normally bolt to the frame right? or do they actually clip to the tow hooks? If you get it and find out that you do need tow hooks, toss an ad up in the classifieds and someone can hook you up for fairly cheap. They just bolt on, very easy install