Will a 2004 ford Taurus front bumper fit a 2003?

Answer 1

Assuming you mean a 2003 Taurus, yes

Actually while the bumpers between 2004 and 2003 taurus will bolt up correctly the two years use a different grille. You'll have a gap between the bottom of the smaller 2003 grille and larger grille opening on the 2004 bumper.

Putting a 2003 bumper on a 2004 the 2004 grille is too big. you can shoehorn it in there or replace it with a 2003 grille.