My new 2018 RAM gets about 17 around town. Towing on our last trip i got about 9.5 MPG, but the engine only about 900 miles on it. With my Tundra 5.7 I was getting 15.7 around town and 8 MPG towing. With that being said the RAM tows WAY better.
Regarding the Ford Push-Rod 7.3, it will not be the miracle engine to replace the diesel, sorry. It doesn’t come close to todays diesel torque, so it will still need to rev like a banchie. Put a turbo on it, and expect to need a 100 gallon tank. The 7.3 is designed to out-do the 6.4 RAM and the 6.3 GMC, period. Bragging rights...