I looked in the Moog catalog. It shows 3 different axles available in that year. The 5000 lb. axle the pin is 6.43" in length & 1.11 dia. It takes part # 8492B or N. The letter suffix stands for brass or nylon. The 7000 lb. axle the pin is 7.89 lenght & 1.25 dia. Part # 8491B or N.
The 9000 lb. axle the pin is 8.75 length & has a tapered pin. It uses # 8462B or N. Moog is available at Carquest stores & many others.