Smell for smell, you've got your hands full. Vinegar may neutralize the noxious gas odor, but then you'll live with vinegar smell until you get rid of that. However, the gas smell is overpowering, while vinegar just reminds you of french fries (in Canada at least). OR, cut out the carpet ASAP, let the truck air out and deal with getting a new liner.

At the end of the day, you'll have a hell of a time getting rid of the gas smell - OK, gasoline smell for all you wiseasses out there