I like driving fast on dirt roads. The occasional gasp from my wife when I kick the rear end loose is like music to my ears. But with the fiberglass fenders (and no fender liner) I get tired of hearing all the rocks dinging off my doors and rocker panels (this old steel doesn't need help with chips and rust). Since I started winter driving this truck again, I also got tired pretty quickly of slush freezing my door seals. So after 5 years of fiberglass fenders it was time to finally make some front mudflaps that extend into the wheel well to protect the door seals and rockers.
After I made a pattern with some cardboard, I picked up a single huge $15 mudflap from a truck stop. This thing nearly extended from one side in the cargo area to the other and is big enough for both guards with plenty to spare.
I traced out the pattern and made sure it fit properly. Then I flipped the pattern and repeated for the other side, keeping the thicker edge towards the outside. Note how it will extend pretty far up into the wheel well to protect the door from anything coming off the tires.
There's a flat surface in the fender well, that if you laid a straight edge on, lines up nicely with the edge of the fender (so without bending, the mudflap will "snug up" to the fender edge). I traced this area out as well as where I wanted the bottom 2 bolts attached, and used my trusty Harbor Freight hole punch to make some screw holes.
Then I pushed the mudflap into place and traced the holes to be drilled for my NutSerts ($15 tool from HF). Here are the nutserts installed after drilling the appropriate sized holes. I painted the edges before install and put a tiny dab of black RTV to seal things up before expanding the nutsert. These install like a pop-rivet, but allow me to use machine screws to bolt the mudflaps in place.
*NOTE* if you use nutserts be sure the nutsert fits snugly into the hole before expanding it, don't drill the hole bigger than you have to
another view - in this one you can barely see the inner bottom nutsert on the other side of the body seam, this was a factory hole and fit a 1/4" nutsert perfectly
a few stainless steel machine screws later and I'm done. With any luck, no more frozen doors and cleaner rocker panels are in my future. I still have to put a small screw eye in the bottom to pull it back and away from the tire a bit (think rally-style), but that's for another day.