ol 55,
What is the frame # ?
What is the VIN ?
Where did you find this VIN number/code ?
The term VIN had no GM-defined meaning for 1955 first series trucks.
GM did not put a code on the frame on this series truck. California might have put a code on the frame (or, required the dealer to put a code on the frame).
F55X is a code that designates 1955 first-series 3100 truck 235 engine, assembled in Flint, MI
http://chevy.oldcarmanualproject.com/chevyresto/55063.htm