If you are only worried about the single-plate issue, stick with a '47 plate and make the argument that the "original manufacturer's design of the antique motor vehicle allows for the use of only single license plates." See below. The code specifically allows single plates for 1946, but also allows it for other years if that is how the car was designed. I would also call a different DMV office. But why not just get a pair of '47 plates?
VCS § 46.2-730
B. On receipt of an application and evidence that the applicant owns or has regular use of another passenger car, autocycle, or motorcycle, the Commissioner may authorize for use on antique motor vehicles and antique trailers Virginia license plates manufactured prior to 1976 and designed for use without decals, if such license plates are embossed with or are of the same year of issue as the model year of the antique motor vehicle or antique trailer on which they are to be displayed. Original metal year tabs issued in place of license plates for years 1943 and 1952 and used with license plates issued in 1942 and 1951, respectively, also may be authorized by the Commissioner for use on antique motor vehicles and antique trailers that are of the same model year as the year the metal tab was originally issued. These license plates and metal tabs shall remain valid so long as title to the vehicle is vested in the applicant. The fee for the registration card and permission to use the license plates and metal tabs on any of these vehicles shall be a one-time fee of $50. If more than one request is made for use, as provided in this section, of license plates having the same number, the Department shall accept only the first such application.
C. Notwithstanding the provisions of §§ 46.2-711 and 46.2-715, antique motor vehicles may display single license plates if the original manufacturer's design of the antique motor vehicles allows for the use of only single license plates or if the license plate was originally issued in one of the following years and is displayed in accordance with the provisions of subsection B: 1906, 1907, 1908, 1909, 1945, or 1946.