A little late, but ...
1955-59 GMC 1/2 ton without 4 wheel drive use a GM F022 front axle. The 1955.2-60 GMC Master Parts Book lists part number 3709756 (casting # 3708831) for both left and right side, just as Dan quoted from the Chevy catalog. Steering arm would be different of course.
The earlier 1947-54 GMC Master Parts Book lists 3696377 for both sides on 1950-54 half ton trucks, but notes "when stock is exhausted use 3709756".
I don't have 1955 first series parts information, but if before and after are the same I would bet that the 55 1st is too.
'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.
| 
