Birchenough Bridge is certainly a highly impressive structure, particularly given its location, but the youthful Godwin was misled by his knowledgeable father. It is not "an exact replica" of Ralph Freeman's other bridge in Sydney, and was only two thirds as long. Sydney's "Coathanger" spans 1650 feet (530m).
Although the roadway is suspended from the arch, this is not a true suspension bridge (where the roadway is suspended below cables or chains hanging in a catenary or parabolic curve): the technical term for this design is a "through arch" bridge.
This booklet (available online) has wonderful photographs of the construction.