[Tx Jim]

To my knowledge JD didn't offer a kit to mount factory toolbox bracket on loaders such as 146. Back when I had a model 158 on my 4255 I welded two 5/8'' nuts to loader mast to attach toolbox bracket.

https://partscatalog.deere.com/jdrc/sidebyside/equipment/57784/referrer/navigation/pgId/11501422

 

[Tx Jim]

Welding either 5/8'' nuts or short 5/8'' bolts will allow bracket to be attached. I also utilized spacers so tool box lid will remain opened once opened.