According to various GMC Maintenance Manuals:
In 1952 engines, 228, 248 and 302 engines all used a pin with a diameter of 0.9898" - 0.9900" with oversize pins of 0.005", 0.010", 0.0015" and 0.0025" (Comment by Hanlon -- I'm guessing that those numbers should either be [0.0005, 0.0010, 0.0015 and 0.0025] OR [0.005, 0.010, 0.015 and 0.025] with the 1st set most likely. The machinists in the audience will weigh in.) Pins vary in length according to piston diameter.
US Army Tech Manual TM9-8025-1 "Ordnance Field and Depot Maintenance" dated May 1958 has the same pin sizes. I don't know when the Army quit purchasing new vehicles with 302 engines, but the next paragraph shows large pins for civilian 302 engines starting in 1956.
In 1956-1960 engines, 270 and 302 engines all used a pin with a diameter of 1.0523-1.0525". Pins vary in length according to piston diameter.
An interesting note is that in 1955.2 270 engines used one part number for the piston pin, while in 1956 270 used a different part number. Same for 302 engines. The Master Parts Book for 55.2-60 shows this, but does not give diameters.
I don't find any GMC pins in the .975" neighborhood that Jay D has.
Questions for Jay D: What is the width of the rod bearing in these rods? Does the locating tang of the bearing fit the notch in the rod correctly?
'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.
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