Depends on your wants/needs. I like having the whole box avail for the "whatever" I toss in it. Others, like to have lots of fuel and less box avail for the "whatever's". Last and current truck, I replaced stock fuel tanks w/ Transfer-flows replacement tank. As stated, not cheap, few hours of time to replace and doubled fuel capacity w/o sacrificing box "space". If you have a short box, a in-bed tank will DEFINITELY reduce things. Not saying you can't. Many w/ long boxes can add a in-bed tank and still have same amount of room left as short boxes w/o tanks.