There is a groove for an O ring on the distributor housing, but since it's in constant motion from the action of the vacuum advance, it would probably wear out pretty quickly. Most of the distributors I've seen don't have the ring there, so I'm going to assume most of them wear and disentigrate.
It doesn't really matter which distributor cap tower is used for the #1 plug wire, as long as the firing order is correct as the other wires are inserted. The correct firing order is 1-5-3-6-2-4 in a clockwise direction. My Motor Magazine service manual shows the #1 position at the cap tower just clockwise from the terminal where the wire to the points attaches.
Jerry
