My 1939-54 GMC Master Parts Book says that your "1574-159069" tag is a "cab or body number" for a 100 thru 350 series AC, CC or EC truck. There is also an engine serial number stamped as shown below.
What is the purpose of the two plastic boxes mounted on the firewall above the heater hoses?
'57 GMC 102, Original 347 V8, HydraMatic, 3.08 rear gear, added A/C, disk front brakes, HEI, AFB carb, '98 Honda Black Currant paint. T-boned and totaled 10/12 '52 GMC 152 Stake Bed, Original 228, SM420, added A/C, HEI, disk front brakes, '67 Chev 3.55 rear gear. Gets used as a real truck.
