[mr48chev]

The in tank is most likely the best way to go in the long run but one has to look at the practical side of things too. One of those is the "how much trouble is it going to be to change the pump no matter where you put it.

A tank that sits on top of the frame or on top of it's special made frame and has to come out the top means you have to remove the bed to access an in tank pump. That pretty well means that you have to figure out how to haul it home or at least get it to a shop where the bed can be removed if the pump fails.

In tank with a tank that can be dropped out the bottom with some but not a great effort is doable in a parking lot as was said above. A pain but it can be done by one guy with a jack most of the time.

External for it's faults or alleged faults can be swapped in short order as long as you can get one without a hassle. As long as it isn't some rare part that can only be had from the outfit that makes it or though their limited vendors you should be good outside of sometimes having to wait for it to come with a parts shipment or on the brown truck with a lot of red label shipping costs.

On parts that can fail on the road but can be replaced and go again like charging units, starters, water pumps, fuel pumps I'd prefer to go with something that was pretty well readily available. Engine, trans or rear end failure means that you either haul the rig home from no matter where you are or you haul it to a shop where it can be repaired if that works better.
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