I have the same problem with my 15 Edge Titanium with 19 inch wheel and AWD. thought the wheels and rims from my 12 would fit so I hiked them up to my ford dealer to change . No go. They where not to sure where I got the wheels but I told them from my 12 Edge will definitely not fit. Been on the internet all day searching for wheels in Canada Cannot find. best I got was from Tire rack in US with Blizzacks and tps for around $1300 US but couldn't find them shipped to Canada.
Would appreciate any info on a Canadian outlet if some one has found using 18 inch wheels