Lots of times the dealers just list the length by the model numbers.
i.e Solitude 384GK-R might be on the website as a 38'. When in reality it's 40'7". Why some do this and some don't is a question for the dealer.
As for the truck. If you're not traveling much then IMO a SRW 1 ton gasser would be the ticket. You may end up in a cold climate area and doing short trips only for several months in a row isn't good for a diesel.
You'll be limited on what you can tow with the gasser though. Max tow ratings are around 15,500-16,000lbs with 4.10 or 4.30 rear end gears. Without those gears you won't be able to tow either of the two you listed.