The 6 cylinder has one bracket (P/N 3877430) and two braces. One "existing" brace for the alternator and one "add-on" brace for the power steering (P/N 3838446). Check out RPO N40 Sheet A2 of the AIM for more info.
For 68 and 69 the bracket is the same (P/N 3877430), but the "add-on" brace is different (P/N 3901807).
Ed