My gut says it will be for F-series and E-series only. Probably not above F450, so no F53 chassis either. The current 5.0L "Coyote" will stay in the Mustang. Plus there are "specialty" versions of the Coyote already available (Trinity, VooDoo, Predator).
It might not make as much horsepower as the Coyote, but I am sure it will have better low end torque.
Being a 2 valve pushrod engine with only 8 injectors will save Ford (and hopefully the customers) a ton of $$$ !