The rotor has pins that are spaced differently on each side, so it can only be installed one way. If you need detailed instructions for distributor replacement, here they are.
Notice: The ignition system distributor driven gear and rotor may be installed in multiple positions. In order to avoid mistakes, mark the distributor on the following components in order to ensure the same mounting position upon reassembly:
Notice: Installing the driven gear 180 degrees out of alignment, or locating the distributor rotor in the wrong holes, may cause a no-start condition. Premature engine wear and damage may result.
Ensure that the spark plug towers are perpendicular to the centerline of the engine.
Tighten Tighten the distributor clamp bolt to 25 N·m (18 lb ft).
Tighten Tighten the screws to 2.4 N·m (21 lb in).