A transfer tank is just that, it is not DOT approved as a Fuel Tank. There is a big difference. We used a aluminum tank off of a Freightliner and cut the length down and then plumbed it into the hose on the fillerneck on the Dodge with a cutoff valve, filter, and a 12v valve. cutoff valve was to change the filter and the 12v valve was on a switch on the dash with a idiot light, this was wired to the ignition. It could not be left on by accident and overfill this way. The vent was plumbed into the factory vent line from the fillerneck, this kept everything clean. In the winter we added a 12v pump because the fuel flowed a little slower. We did this so we could run to Moab together several years ago since I held 150 gallons. A friend of mine paid a $1,000 fine for using a transfer tank in Tn. plumbed into his . Check the price difference between a transfer tank and a auxillary tank.