Looking for advice

[earnies2]

I now have a 2009 prostar with 800k on it. The truck is getting only 5.5 mpg, and it was built for Werner to haul a 3 axle papper trailer so it's heavy. And the fact that it has 800k on it I don't want to rebuild it. That being said I'm looking to update into a 2018-2020 truck.
I like the Mack Anthem and the Freightliner Cascadia I am also looking at International LT. I'm having a hard time deciding and trying to find one with a 13 speed trany.
Should I settle for a autoshift?
What say you on a truck and specs.. I'm looking for fuel millage,light weight and a 240 wheelbase. I pull a flatbed out of Boston as far west as Texas