Crank and rods are all the same. F had stronger rod bolts that will fit in the old rods. The Sandcast head and early K1 are the best as far as power from the factory, later heads got less attention and the port shape accuracy got very bad in the mid and later sohc. The best thing you can do to any sohc head is clean up the ports and smooth out the sharp edges in the chambers. If you are going to have port work done or bigger valves installed it doesn't matter what year head you start with. The very earliest cams are by far the best, the later the head the less accurate the cam timing became. Cylinders before K3 had a slightly shorter cylinder compared to the K3 and later. The earlier ones are more prone to oil seepage because the later ones came with extra rubber seals around the oil return passages. The earlier the parts the better as far as I am concerned.
