A 48C will not fit, You would need a 48-in. (122-cm) Edge™ Xtra Deck
http://www.deere.com/wps/dcom/en_US.../x300_48in_deck/x300_48in_deck.page?#viewTabs
For $600 to $800 more you probaly could have got a X320 which comes with a 48" deck..........are you still in the exchange trial period where you can upgrade?
http://www.deere.com/wps/dcom/en_US.../x300_48in_deck/x300_48in_deck.page?#viewTabs
For $600 to $800 more you probaly could have got a X320 which comes with a 48" deck..........are you still in the exchange trial period where you can upgrade?