Well...this is what the front of my T-100 looked like before I started. I had just finished polishing my headlights. Yers are in need of some polishing, too!
As you can tell...it's not much of a front end to work with. The frame has some extensions that will always notch out the front air dam if you bump into something...as you can see on the left side of the truck. So my first thought were to drop it down so it wouldn't do that...thus my modified air dam started the whole business of my aerodynamic research on my truck. Also, the filler panels can easily be removed to git access behind them. If it was a solid piece...I'd have to remove the whole air dam just to do some work.
I believe my MPG numbers should validate a belly pan fer trucks if yer road use allows you to drop it down some. The big difference was the rear pan/diffuser in the back.
Yer Ford Ranger has more to work with. I would try some sort of inexpensive covering that you can form fit over yer bumper (like aluminum flashing) at first to git a basic form shape and validate some numbers fer you. Start out cheap and then move to the more expensive stuff. Then you can move on to the belly pan...
