Wow, I am truly impressed.
You are my kind of guy, you go past just talking about something and go out and do it. A lot of people don't do anything beyond the talking phase (I'm worse, I don't always get past
thinking about stuff).
You have given me a lot of ideas for my '89 Subaru GL 4x4 Wagon. Similar underside at a different scale. But it still has 9 inches of clearance underneath with lots of stuff hanging down. Unfortunately, my halfshafts are spinning in the air instead of running through tubes, so your sweet idea of tripping the airflow under them isn't applicable. But I will definitely look into attaching some sheet metal to the factory skid plate for airflow. Airdams just don't work the same on 4x4's, too much air rushing underneath the vehicle elsewhere.
P.S. - Your vehicle will have a MPG sweet spot where the engine is operating more effeciently, even if you are pushing some more air at a higher vehicle speed. That's what's nice about the scangauge; you can see where you are getting the best efficiency instead of blindly applying slower is better (which is true 90% of the time
).
And the mechanical fan is a BIG draw of horsepower (think 5-10 hp+). You can get one of those metal flexing fan blades from Summit racing that lower their profile when the revs increase, you still push air but with more efficiency. And the grill block can harm you if it makes the clutch lock up more for the fan. Best case scenario is to get single or dual electric fans that run off A/C signal and/or a thermocouple.