JBA is the engine serial number preface that refers to a 216 engine in a 1951 3100 assembled in Flint, MI
http://chevy.oldcarmanualproject.com/chevyresto/51053.htm

The 3100 hood side-emblem was used from late 1949-1952.

The passenger door is a 1951 door.

The lack of a driver's side cowl ventilator started in 1951 (51-55).

The driver's-side rear-view mirror arm is correct for a vent-window door (51-55).

Is there a vehicle ID plate between the driver-side hinges on the cab?

Tim
1954Advance-Design.com
1954 3106 Carryall Suburban
1954 3104 5-window pickup w/Hydra-Matic
The 216 and early 235 engines are not "splash oilers" -- this is a splash oiler.