What year expedition are you considering? The 15-17s have the option of the integrated brake controller which is included in the HD tow package but can be added if not equipped by snapping the module into the dash and having a dealer program it to the truck. Then you'll just need a 7 pin connector wired in. But if it were me I'd just limit my search to vehicles with HD tow package, since prior to 15, an EL could have 3.31 gears or 3.73 gears and you want 3.73 for towing. 15-17 ELs all had 3.73 gears with the ecoboost engine but may or may not have HD tow. If they have the round 7 pin connector on the hitch, they have HD tow package.