Hi,
See
Search: CarSeatData.org - user ratings of carseats fitting into cars
You'll have to scroll to the bottom for the current year info. I'm not sure what year Ford changed body styles, but several have had OK-Good success fitting
Boulevard's in the back seat (which are larger then the
Marathon). If you click on the listing, there will be notes about the install. Seems center is best because of limited room. Either way, make sure to have it checked and/or installed by a CPS Tech, just to be safe!