I searched all over the net for a systematic procedure to install a '67-'68 Mustang rocker panel molding but as usually happens, I did not find one that answered all my questions and specific issues. But in the end my efforts were good and after minor complications, I was able to install my car's original factory accessory rocker panels. Modern reproduction panels are about $35.00 each, but the quality is very questionable, so I considered myself very lucky to have the originals in such great condition that all they needed was a 0000-steel wool rub to bring out the shine. The Dynacorn-brand molding clip set is about $15.00 is of excellent quality, and brings all necessary clips for both sides and rivets.They fit perfectly (for a change!)
I had to use extra rivets from my kit since I snapped a few of these broken during the install.
Some folks initially think that the small tab on top of the clip is where the molding snaps into. This tab is to keep the molding from rubbing against the paint, and eventually scratching it. The molding snaps on each of the four lips of each corner of the clip. The problem is that sometimes you have to massage the molding to make it snap tight against the clips.
The front bracket holes in the right fender were covered with body filler, a minor complication. So I accessed the holes from the inside of the fender. Once I located the original holes I took a smaller diameter drill bit and with my hand's index and thumb, began "drilling" through the filler from the inside out. Once the panel was drilled through, I completed the hole with the right diameter.
Use the metal bracket and screw (included) to attach this clip to the fender
Then I followed through with the remaining smaller holes (5 in total) for the brackets on the fender.
Place the molding against the bottom side of the clips as shown, and then snap together the top side. Once all clips were fastened, the molding was test-fitted. Most of the clips snapped ok, except for a couple, so I had to remove the molding back out and carefully and evenly pull the sides close a bit at a time to make everything snap together tight.
grab it like this and compress...
And try again until all clips snap tight
It took me about 1 hour of planning and rehearsing the steps, and about 2 hours to do both sides. The final product should look flush without any bends (where you compressed), and should feel tight.