1. Here's what you need for the restoration, in addition to the pancake housing and clamp: One Sylvania 4411 sealed beam, and one reproduction headlight gasket.
2. Trim the rib off one edge of the gasket as shown here.
3. Remove some of the alignment key on the back of the lamp with a belt sander. Be sure to go slowly to avoid heat buildup or damaging the light.
4. After removing the alignment key, wrap the bulb with the gasket, trimmed side in. Load the bulb into the housing, making sure it sits flat.
5. Install the clamp, adjusting the bulb position as necessary to obtain a proper fit.