L54T016958 (Vehicle Identification Number)
L = 3800 series truck (1-ton)
54 = 1954 (model year)
T = Tarrytown, NY (location of assembly plant)
16958 = production number (16958-1000 = 15958th truck built that model year)

0205646-T54UB (engine ID: engine "serial number")
0205646 = 204646th engine built (this seems high?)
T - Tonawanda (location where built)
54 = 1954 (model year)
U = 235 6-cylinder engine, 112 horse-power, 1-barrel carburetor, Heavy Duty transmission (I do not know if this meant 3-speed and/or 4-speed)
B = 3800 series truck (1-ton)