John & Jim,
I'm not sure what portion of this thread to post this in (Reb or Yank branch), but perhaps it might help to think of this as a company or small battalion rather than a regiment? Names like "Corcoran's Guards" are more typical of company noms de guerre aren't they? And the MSG listings I've seen early on frequently list various company commanders that later became regimental commanders. Assuming that the original Corcoran personage is permanently lost, is there any common thread on the MSG side that might point to where the few men listed would have been recruited from?