Auxiliary Diesel Tank Gravity Feed vs. Electronic pump

Aftermarket replacement of the OEM tank would be a plan, but still some $$$. There are a couple of good vendors out there. The increased capacity would still take away from payload, but not as much as an in bed tank if it's large capacity. OTOH, if you're looking for extreme driving range on a full fuel load, the in bed tank in combo with the OEM tank would give you way more range than replacement of the OEM.