Maybe they are- cuz the cross bolts are almost 4'' long, they run from side to side thru the frame rail. There is also about an 1 1/2'' long bolt that comes up from the bottom- thats not the one im referring to though.
-Steven
On the OBS trucks, The tow hook is threaded and there are 3 (IIRC) small bolts that go through the frame and bolt directly to the hook itself (Not Through)