John Deere offers four options for mounting the toolbox. Behind the seat, right side of the platform, right frame rail, and loader mount frame.
I choose behind the seat. With a loader the right frame was out. Since I installed right side steps, the right side of the platform was out. I did not like the way the toolbox stuck out with the loader frame mount or the price of the mounting bracket.
The toolbox has a bent metal piece on the back that hangs on the beam. The beam has a tab that goes thru a slot on the back of the toolbox. There is a pin that goes thru this tab, then the toolbox tray goes on top to keep the pin in. The beam was $55, the toolbox $48.
I normally like to keep the hardware on the tractor all metric, but I had the 5/8" bolts, washers and nuts. JD wanted $22 each for the two spacers, so I found some 3pt hitch bushings at Tractor Supply for $2 each.