I have 2 of the original Trans Am axles for the 67-69 Camaros. The part number was 3927508. These were purchased years ago. They are for drum brake rear ends. They did have 1/2 inch wheel studs (knurl diameter .6125, knurl length .24 (.32 to the stepdown by the threads) and the overall length stud length is 1.54 inches). On the axles the diameter after the machined surface for the bearing 1.36 and the diameter by the machining for the splines 1.15. The axles use c-clips. The overall length of the axle from the wheel surface to the c-clip end is 29 1/2 inches. I have no idea on any differences with heat treating. I don't have a stock axle to compare these axles to so I tried to list all the important dimensions.
I hope this supplies all the information needed.