I looked thru four 2" binders of GMC Service Bulletins that I have (mostly '55 up thru '62 with a lot of duplicates) with no luck. No luck looking thru the indexes for those same years for mention of distributor gears.
I did notice the phenomena that jimgmc mentions above where I have a 1953 Service Bulletin that has an illustration identified as "TP-xxxx" and an Oct 54 Service Bulletin with an illustration identified as "TPM-1711". Assuming (hate that word) that the TPM numbers were issued in sequential numbers, the drawings in question (TPM-1344 & 1346) would be between 1953 and October 1954. The later into my set of Service Bulletins I went the higher the TPM numbers were.
Didn't find any applicable info on OldGMCtrucks forum either.
'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.
| 
