Yes a backhoe can be added at anytime on the bigger tractors.
Just a note: You really need to put the L suffix on the # when you talk about your tractor, So L3240HST (2007-2009) or L3240HST-3 (2010-)
or if cabbed L3240HSTC (2007-2009) Or L3240HSTC-3 (2010-)
Make it a lot easier to get right parts and advice.