The 4.7L and the Sohc Fords are closer to 40's BMW tech than anything modern.Yes they have modern fuel and ignition systems but that is all.2007 4.7L and up uses a poly chamber (yes that poly) and dual spark plugs. Hemi is much cheaper to build and I mean much cheaper.
GM noted this and did not build a Sohc V-8 instead building their LS series.Modern,light and powerful (torque) pushrod V-8's.
Overall the LS and Hemi are more efficient than the overhead cam designs.Remember these all were built to power a heavy truck and that also limits the fuel economy.
Lastly a small hemi (5.0L) would have been a great idea but the new V-6 does the same thing with only a small torque and h.p. loss without building yet another size Hemi.BTW 25 hwy mpg with the 8 spd in the truck.Not too shabby.