Never had a 7.3 but my last 2 company trucks have been a 5.0 F150 and 6.2 F250 both 6 speed autos and while both were good trucks overall IMO the 5.0 out towed the 6.2 and got better mileage across the board.
My 6.2 averaged 8.5 mpg on a 2400 mi tow with a 4000lb enclosed single axle trailer and 1000 lbs in the bed and a lot of the drive was slower up the Alcan during breakup with all the frost heaves. All in 2wd except a couple hundred miles.
Empty hiway/commuting mileage 11-12 mpg.
Even with the small trailer it was a 2nd gear wound up to 4-5k rpms trip up every hill to maintain 55-60 mph.
I don't think they are good towing motors personally. Good overall truck with poor mileage compared to the other new gassers.