[Ronbo]

Your wire between the coil and distributor may be broken down internally. (common with carbon core wires)

Cap and rotor normally come as a set. I would check the center contact carbon ball in the cap to make sure it didn't fall out. (again common problem) Your rotor will have a spring loaded contact to the center cap pin, this should contact the cap pin and can be checked by placing a small piece of clay on the contact then install / remove the cap and see if the clay is completely penetrated.

You've got a gap somewhere in the path to the plugs that's large enough to make the jump to the air cleaner an easier route...