Congrats on your new toys!
I deliver campers all over the US and have logged 467,000 miles in the past 4.5 years. You will have no trouble finding ULSD and by all means please do not use anything else in your particular truck. The fuel I prefer is Flying J which is used 99.9999% of the time in my truck and I have never had an issue with it, not saying it can't happen. Go to Flying J
for current daily diesel prices at each Flying J location. One of the better features of Flying J is they cater to the RV'er by having an RV island with sewage dump which is separate from the car and truck islands and there is also dedicated RV parking. You can also apply for one of thier rewards cards and get a few pennies off each gallon of fuel.
Have a great trip!
TV1: Black Sheep, 2001 Dodge 3500, 800,xxx miles, a few non-stock parts here and there...
TV2: Brownie, 1989 Dodge W250, only 256,000 miles!
TV3: 2004.5 Dodge 3500, 415,000 miles, 6 spd
TV4: 2005 Dodge 3500, 478,000 miles, 4spd auto
"Too much of what I once knew I now know not" Me