If you find your old 1990's work ute not travelling quickly down the quarter mile and you thought removing the tool box would help, my suggestion is to look elsewhere too....
The other day I had to adjust the hinges on the door and removed the fender only to discover the old ute was hoarding about a litre or more of dirt and crap inside the guard. Obviously it had done the odd trip on unsealed roads, but still the amount was surprising. There was no sign of rust as one would expect where dirt and likely water would collect behind the guard, so no warning bells, however the bolts on the bottom did snap. so I need to remove them the hard way.
I would hazard a guess the other side is similar, so perhaps worth a few minutes loosing the guards to get rid of dirt build up if you do a lot of off road driving.
Job is not hard, and takes about 10-15 minutes to free the guard and then the dirt drops out easily, unless of course the bottom bolts snap....so perhaps a good dose of rust spray before attempting the first time or be prepared to remove the harder way. On the passenger side just watch your antenna... but otherwise there is no hidden bolts or difficulty in losing the guard enough to Free Willy - I mean the dirt!