Jim,
The 54/55 GMC Vehicle ID plate was riveted to the door driver's frame between the hinges (with two "pop in" rivets). GM/GMC did not stamp an ID on the frame in 54/55. In some states (like CA) there might have been a stamp placed on the frame after/at delivery/registration.
GMC did not designate trucks by years, they designated series: Z series was approximately 1954/55 New Design truck and they had the one-piece windshield. Unlike earlier Advance-Design Chevrolet trucks and New Design GMC trucks which had similar dash designs/equipment, the Z-series dash is quite different from the 54/55st Chevrolet truck dash.
The light truck transmissions and rear ends were the same for GMC and Chevrolet. Do you have an open drive-shaft (late 1955 Z-series and 1955st Chevrolet) or an enclosed driveshaft (1954 Chevrolet and early GMC Z-series).
What is your strange ID number?
(ID code/serial-number that is on the certificate of ownership)?
Post that code here and we can help you speculate on its meaning?
Here is excellent information from Rob English:
http://www.oldgmctrucks.com/page0009.htmlhttp://www.oldgmctrucks.com/page0010.html
