May buy a new 2008 left over expedition King Ranch, but it doesn't have the HD tow pkg. While I don't tow, I drive 100 miles per day highway with steep inclines. Is this a concern with heating the transmission and engine, or am I better off finding one with a HD tow pkg which includes bigger radiator & trans oil cooler.
Well from reading your original post if you don't tow you don't have to worry about any of that. Even with steep inclines the stock set up should handle it just fine. I would still do the aftermarket trans cooler though. A cool trans is a happy trans.
The only items in HD Tow I'm aware of are the slightly larger engine coolant radiator, the larger transmission cooler, and the seven pin wiring to the rear of the truck.
To my knowledge the alternator and battery are the same in all Expeditions.
HD Tow still has the 3.23 (?) axles in '08 and later. My '07 got the 3.73 as part of HD Tow, but I think that's now a separate option.
Transmission heat is a killer but most heat comes from the slippage during shifting. The Expeditions seem to lock up pretty quickly, even when towing.
If you're concerned get the Interceptor OBD2 gage, set it for transmission and coolant temperature, and put it on your dashboard. I doubt you'll note excessive temperatures but the gage will let you know what's happening. Just plugs into the OBD2 connector under the dash. Mine is just velcroed on top of the dash in a cheap pod.