I was told about a recent ebay auction which featured some very rare NOS 12-bolt axles designed for heavy-duty use and Trans-Am racing. These were listed as part number 3927508 in the Chevrolet Special Equipment catalog (aka Green Sheets). These axles are a rare find and are real GM parts, not aftermarket. They were meant for 1967 - 1969 Chevrolet Camaros with rear drum brakes and utilized 1/2" studs (per the catalog). The axles are stock length as well as the spline count (30). The casting numbers on the end of the axles look like they are 9145 and 9349. Below are some photos of the actual parts.