I would love it if Toyota would make a proper 3/4 ton

Must be a new daffynation for "Ramcharger" eh?     .

Depends are what you are doing with it but a low mile pre 2022 Tundra would my pick. They are built heavier than a traditional 1500 and last. I'm a fleet mechanic and see them all.  Newer engines have issues, mainly because of government emissions standards. 

Ya around there, my best was 13L per 100   it gets cut in half at a minimum when towing heavy, but man does it ever tow nice!

I had one of the 1500HDs years ago with a 6.0L and it was absolutely brutal on fuel.     I bet 18L/100kms empty would be very optimistic.