From what I’m reading the majority is aluminum except the frame, roll cage, and floor pan. Pretty easy to spot the rivets in the aluminum sections. Just a note I’ve been in aviation over 20 years so it’s nothing new to me. Ford hired one of Boeings production engineers to help develop the f150...
If you don’t plan on doing any major water foraging you can gain alittle mpg by removing the splash guard in the box. Saves you the $300-$600 for an aftermarket intake and still maintain your accessibility to change filters or service them without removing the whole box.
Can’t tune for methanol with a ford tune. You would need a custom tuner to do that I. Which right now you’d have to go to Canada for at the moment.