Nathan,
That Fergus plate looks wrong to me. I have Fergus plates on two of my cars (1959 and 1961) and the Fergus stock numbers are completely unrelated to Morgan chassis numbers. (They are much higher.) It looks to me like someone acquired a reproduction Fergus plate and stamped the Morgan chassis number on it.
If your car still has the original chassis frame, the chassis number should be stamped on the cross-member under the passenger seat.
