They made bed extensions for the 3520A. It's the same one for the B and C series The 3520A does not have the legs bored to accept the bed. That came out with the B series. The castings are also thicker in the area where the lowered bed goes. I addes a steel plate to the inside of my legs to beef it up and take the threads better. Since my bed would not go exactly where it does for the B and C series I made my own tool post extension. That and I'm cheap.