Hello,
On the 732 you can have 3 kinds of oxygen bottles. 39 cubic feet , 76 or 114. As far as i know these are the ones used, but there might be other ones also. According to the number of crew using oxygen and the temperature of the bottle you get the required amount of PSI. Ask your operator technical department if they issued a service bulletin regarding these requirements according to the kind of oxygen bottles fitted in your airplanes. Check also the requirements for the passenger oxygen bottle, that is normally a 114 cubic feet one with a minimum dispatch pressure of 1400 PSI.