You will have to use a diecast. Matchbox and Maisto have done 1/24 1999 regular cab F350's although I've been told the Maisto is really closer to 1/26. Testor's made a kit version of the Maisto diecast with a pickup, flatbed or stake side.
As far as the powerstroke, join the club. A parts pack with either a Powerstroke or a Cummins for the Dodge would sell well based on the people asking about them.