Jerry: 1939-53 GMC Master Parts Book lists one shaft specifically for HydraMatic equipped trucks. Part number is 2293665. But it is lumped together with 7 other shafts that are described to be around 60+ inches long and a drawing of a traditional driveshaft, so I suspect it isn't what Roscoe (the OP) is looking for.
'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.
