a 12 gal with anEDC would be more than suffcient... and you can either put it in your bed or hide it under.... its all your preference... thats why its called customizing... hell you could bolt it to your roof if you wanted.... not that it would look good/ be feasible or anywhere near intteligen...but you could do it if your heart so desires.
towing is no problem if you build it for that. SD has some strong arms as does outlaw, got to build one for my dually cause of my narrow ass, but with 15000 lb with of lift I can do with mine, towing is a breeze.