This is like music to my ears. If I could get anything near 20 mpg out of it on my way back from Colorado to New Hampshire, I would be really happy. Great to hear that a Ford guy could be happy with a Cummins rig as well... that honesty goes a long way. Also happy that you think the AEV stuff is nice. I bought the truck sight unseen, with my buddy inspecting it for me. So, I still have a little anxiety about it being all that I hope.
I live at sea level and it's flat so that probably goes a long way towards the fuel economy but if you don't have your foot in it all the time you should be getting 16+ easily on the way home. I still prefer the Ford cab/interior to the RAM but I am quickly becoming a Cummins fan boy and it's hard to deny the heritage and track record of the motor itself. The AEV bumpers and wheels are top notch stuff, I'd much rather have a Carli or Thuren lift but their bracket setup simply works for an everyday driver. You can easily upgrade the suspension along the way should you feel that you need more from it than what the AEV setup can provide. You shouldn't have any fears in buying that truck and know that you'll get top dollar on resale in that configuration should you find it's just not for you.
Off topic but is that a Doberman or Rottweiler in your profile pic? We have three Dobermans, big fans.