I would also recommend Transfer Flow aux fuel tanks. I used to sell them, top of the line, top quality, DOT approved and safe. They aren't cheap but compared to others I used to sell they stand out above all. What makes them more expensive is the pump system to keep your main tank at a preset level. They are made in California so they meet some rigorous testing.
2014 Palomino Puma 25RS
2011 F-150 Super Crew XLT
Days camped in 2014 - 23
Camped 2015 - 47
Camped 2016 - 51 done - 6 more planned so far