We use the Sovereign II body and reduce the height of the feed tube to accept our new clamping feed-neck. The rest of the marker is all Sovereign III. The Sovereign II body takes it's own barrel thread and there is a choice of three Spyder barrel adapters at .686, 688 and .690.
The Classic STP bodies are quite rare. We only have a few vertical and right-hand feed bodies that take the original Sterling thread. We have plenty of new STP bodies and barrels available. :-)