Correct. The trucks with the gas tank skid don't have the studs on the hanger straps. Those are for the plastic gravel shield that the non-skid plate trucks get.
The bolts along the rear of the skid, into the frame, go into thread-serts (a.k.a. riv-nuts). Most likely you'll have to grind or drill them out anyway, because the bolts rust into the thread-serts, then when you try to unscrew them the inserts just spin in the holes in the frame. They're great for assembling the trucks on the assembly line, but an idiotic idea overall. Impossible to service in the field.
now wait...my truck has no skids or goofy plastic covers...:( i think i got haggled -_- i don't even see places to put on skids :-/