What kind do you have now? Why don't you add things to upgrade what you have now?
Call Watkinsville Golf cart 706-769-2095. Talk to Dave
He did the high amp controller and high amp motor for mine. I left mine as a 36 volt.
Go to Carts unlimited and get yourself an alltrax controller with matching silonoid and keep it 36 volt. When I changed the batteries in my 48volt cart I was asking about the difference and guy told me that most people prefer 36 volt. I do know a 36 will stay charged longer than my 48.
Can you tell a big difference in your cart after changing?