Well after sleeping on it, yes I remember exactly what the carbon center is like in the MSD cap, it basically just "plugs in".
Chapper, this cap was relieved a looong time ago and yes it was in place but can't say exactly how long it's been missing.
Bonefish, I drove it around the neighborhood and in the garage at the least like this That's the last time the cap was off and I didn't find it on the trailer floor either
More than likely its laying in the bottom of the dist body.. if it was even slightly loose it could vibrate around and wear the sides and fall out as soon as you lifted the cap