If you are looking for diesel power, the E-series still ships with the 6.0
Our local and regional ambulance are using a different service provider
(read that as cheaper) so I can't speak with much authority regarding the
current crop of 6.0s. Ford still appears to be the bus of choice and, of our
local EMS providers, none have approached us for warranty repairs.
We are a light duty dealer and don't handle anything bigger than F550.