I would tend to the HD package. Looking at the spec sheet, it looks as if the Expedition standard has no option for a radiator upgrade. A trans cooler appears to be optional on the HD package, but not offered on the standard package. It looks as if you'd have to do a lot of aftermarket upgrades to the standard package if you wanted better cooling capabilities.
Do some research into the Ecoboost. Check this guy out. He seems to know what he's talking about.
https://www.youtube.com/user/FordTec...query=ecoboost
(Don't dismiss the Chevy or Chrysler equivalents)