It’s possible for even DRWs to sway. There are lots of potential problems like putting too much air in the air bags, worn shocks, no sway bars, low tire pressure, worn bed spacers, improper tie down tightening, etc. I say etc because I probably left something out.
If you get a DRW long bed, you won’t find a TC made for a long bed that won’t work unless it’s an old TC on a new truck with a cab that is too tall or tailgate that is too narrow on a few trucks. The longest heaviest models with basements being the worst handling and the nonbasement shortest lightest being the best. Another complication is most of the largest TCs can have double or more of the fresh/grey/black tanks which just adds even more weight if they are full.
I’d probably consider a gasoline engine unless you plan to tow if you are thinking 10 years or older. Many of the diesels are very expensive to fix.
