I would second Stephen's judgment here. Goodwin & Gulick was my first reference grammar also -- and it is good -- but Smyth is really so far superior. On the other hand, although I've never consulted it, Goodwin's Syntax of the Moods and Tenses of the Greek Verb is an "oldie but goodie" (3d ed. 1867) that is readily available for download at Textkit, accessible at Google Books and the Perseus site, and is even part of the free Perseus collection at Logos. But on matters of Greek syntax, I would turn first to Rijksbaron.
Carl W. Conrad
Department of Classics, Washington University (Retired)