SIMPLE ANSWER IS YES it can be converted. Do some research on site for others that have done the change over before and can save you lots of mistakes and expense. This might also be the time to think about going to 48 volts as well? By adding two more batterys and by changing solenoid anyway you will only be adding two 6 volt batterys and a 48 volt charger as an extra expense.
Just my .02c worth?