Yup DY-100s. Of the ships I drew, they're the only ones that actually appear on the cover art. A few of the other ships are from the animated Star Trek, so they didn't make the cut. The Star Trek III Merchantman is probably too hard to model.
I think the 47 was not an in-joke, but I'm not sure how it was chosen. I might have been told, but I've forgotten by now.