RE: Additional fuel tank
Ck out “Transfer Flow” fuel tanks. I bought their 50gal./ 10 cu.ft tool box combo. Great fit and finish and their made in the U.S.A. ??
RE: Additional fuel carrying capacity on pickup
https://www.transferflow.com/ Ck out Transferflow tanks great product. On my 2017 F350 it sits level with top bed rail. Mine is a 50 gal/ toolbox combo. Quality build and the best part it is 100% USA made and sourced.