Step 1: Sketch:
The region lies below the line $2x + 3y = 6$, above the line $x + y = 1$, in the first quadrant. It is a quadrilateral.
Step 2: Pick the extreme corners:
Since $z = 3x + y$ grows fastest in $x$, the maximum is at the corner with the largest $x$, namely $(3,0)$, $z = 9$. The minimum is at the corner closest to the origin in the $y$ direction, $(0,1)$, $z = 1$.
Step 3: Difference:
$9 - 1 = 8$.
Final Answer:
The difference is 8, option (C).
\[ \boxed{8} \]