If you have the OEM model you are probably missing the major part of the rack. There is a quite a bit of rack structure that going under the skin of the 451 if I remember you need to remove the back end plastic and add the internal structure that the basic rack for one or two bikes mounts to. That's one of the reasons most of us purchased a hitch type solution. Good luck and I hope I'm wrong.
The two pieces are not very big, but do require taking the rear "CBS" off. I quote CBS because somehow I remember that, but don't remember what it stands for. Basically you have to remove the side skirts and then the rear bumper, which IIRC requires unscrewing the rear hatch bottom. I still recall my son telling my dad that I was actually "crying" during the install... One needs to drill 4 holes for each of the brackets. There were screws provided that needed to be torqued to a specific value. If it started to give, then pop rivets could be used. My EPC subscription just ran out, but I tried to take a peak for the parts/part numbers just before it expired and didn't see them....
Sorry about that. Lots going on. Probably find out today whether they total my smart or not. Geez it took a long time to estimate the damage.....
