There are all several differences between those two (F2 and K discs). If a dual disc set up is your goal, the easiest way to accomplish it is to swap the entire front of a 1975-77 GL1000 (triples, forks, brakes, rotors). You can also swap the entire front or selected portions of the F models. Swapping the entire front ensures compatibility with offset (spacing/alignment of brake rotors and calipers) and avoids the needs for shimming.