In the original story shaft was white. They made him black in the movieShaft being black is part of the character.
The Scarface in the 30s was an Italian during the bootlegging era in Chicago.
The Scarface during the 80s was a Cuban coke dealer in Miami.
Scarface‘a character isn’t tied to a race.
The two previous movies have been a reflection of the drug era of the time.
"In Tidyman's original story Shaft was white, but [Gordon] Parks cast Richard Roundtree as the eponymous hero."
Shaft (1971 film) - Wikipedia