I have had my rotor off quite a few times in the last few weeks. I changed to a Pertonics ignition system, (See thread about coil problems, it's under Stock, ("Not again!"). I have found that the distributor shaft has a flat side to it at the top. The rotor also has the same flat spot under it. Just remember which direction your rotor was facing before you removed it. Hope this helps you out and hope you get your problem fixed. These trucks are definitely a labor of love.
militarypotts Spec/4 Military Police, Vietnam Era, "Does the noise in my head bother you? Welcome to the Twilight Zone!"