As you all may know, Brazil has some odd things... The local automotive market was very closed during the 80s, and since there were few factory options many customers resorted to aftermarket mods such as those fancy double-cab conversions. Often, in order to differentiate more from the stock versions, a more rounded front clip was also offered for the F-series which had retained the bodystyle introduced locally in '72.
Still not the best reference for aerodynamics, but not as brick-shaped as the stock one...