[donut]

If I didn't have a stock fan come apart as a teenager, I might thing the same thing. (came apart due to damage by me or PO?)
The truck ran into problems when I got into the city, not the highway.
If GM has an issue, there would have been a recall to install fans, air dams, etc. Hundreds of thousands of these trucks without issue have run up and down the roads. Frontal area should be more than adequate.

Look at it realistically. Air will flow under. It will flow over. Air hitting square will flow to the path of least resistance, which is through.
I have had to cover a radiator that was over-cooling. Picture big trucks in the winter...