The question is an interesting one considering that North Korea just showed that it can reach the West Coast. And Iran and North Korea have a technical cooperation agreement so that Iran gets its place on the technology pipeline.
North Korea now has 6,200 mile strike capability. And if Iran gets the equivalent capability, that would put the East Coast of the United States in its sights.
On the Shahab timeline, that New York City killer would be the Shahab 6. The Shahabs are based on North Korean and Chinese tech and improve incrementally. Estimates for that date vary from 2015 to 2020.
Iranian missile development has gone forward in Kermanshah, in Iran’s west, a good distance away from Tehran, and close to its border with Iraq. The distance between Kermanshah and New York City is just a little over 6,000 miles.