I just pulled a driveshaft from a 62 Cutlass for comparison. Ken and Jim were correct about the Cutlass having a smaller driveshaft. The back section between the 63 4 speed Jetfire and 62 automatic Jetfire driveshafts are the same. The front section between the Cutlass automatic and the Jetfire automatic are the same. The Cutlass back section is much smaller diameter. An automatic front section is the same as the 4 speed other than it is shorter so the auto front section could easily be cut down for a 4 speed.