What year F frame are you thinking of using? I can only speak to the 77/78 frames, never seen a 75/76.
OS is right, the seat won't work either. The k models had a triangular brace (not really a brace but...) welded on to the back of the frame for foot peg/exhaust mounts (well the 77/78's did). Also some brackets on the brake side will be different as the F's are rear disk. There's a mount for the master cylinder and the brake stay is in a different spot.
So it can be done, but there will be some work.
I think I have some pics...first two of a 78F, second set of a 78K