You might want to look under your truck, only the front vertical bolt goes directly into the body. The other 2 vertical bolts go into the Ford-installed brackets that your truck came with. The above picture is from my Badlands. The picture shows the Ford-installed bracket that my truck came...
There are 3 places(4 doors) that mount to the body/frame. The front mount bolts directly into the body, the other 2 bolt into the bracket you see. That bracket bolts to the pinch weld and the frame.
The brackets where the horizontal bolts attach to the body are only on the factory equipped trucks. Without them there is no place to bolt the rails to the body. You would only have the pinch weld bolts holding them on.
Installed the Zroadz sliders. Great quality and an easy mod. They are heavy so help from a buddy wouldn't hurt. I did notice 3/4 of the factory slider nuts were only hand tight and a couple were almost off the bolt. It would be a good idea to check the factory nuts.