I have a GC2300 and took it to the dealer to have a backhoe installed. He also sells trailers and I asked what size I should get to haul the tractor with hoe and FEL attached. He suggested exactly what ultrarunner said (16', dual axle, brakes) and that is what I ordered since he didn't have it in stock.
Hopefully it will come in before the work is done because I know my 8' single axle trailer that I used to get it there will not do.
Of course I need to get a couple more straps for the backhoe.