The Total Cost Involved 1965 Mustang coilover suspension comes with a new heavy-duty cross member frame piece with the motor mount ears, lower control arm mounts, and power steering rack mounts in place. Installation is just a matter of slipping the cross member in from underneath, up against the locating plates and carefully welding around the contact points.
In reality though, it didn't go as smooth as that. The instructions say that the ends of the crossmember may need to be trimmed to fit. My reinforced frame rail spacing is 27 1/4" and the crossmember is 27 3/8th " so I had to trim about 1/6th inch off each end. This was easy to do once marked up and attacked with a grinder.
Once the grinding was done, the dimensions were equal so it took a little pounding to get it in place and ready to weld.