Your tractor is a later 550. I think 1962 was when they changed to that style pump. The reservoir to which the fill cap is attached is stationary. The bracket that supports the pump is slotted alowing you to move the pump and tighten the belt. It probably has beenclose to 35 years since I have done one ,but we always did that if we had the hood off. Right now if I remember correctly you can do it if you take the front shell off. What is the serial number of your tractor?