https://www.ruralking.com/king-kutter-48-tiller-tg-48-xb-0
Yes, will it fit a QH? No not without minor modification. I had to buy longer implement pins, used washers for spacers and added QH bushings. Compare the top link attach point, I moved spacer to front hole and bolts to the rear frame holes.
The PTO shaft length will need to be sized to your tractor. Tractor mike and others have youtube videos on this.
Others can chime in, I think your BX could handle 5' my mods shouldn't be needed on larger tiller.
When you say it won't fit a QH without modification, I assume that means a BX2380 with the quick hitch? How do you think it will fit and run behind a BX2380 with the standard 3 point cat 1 hitch? Thanks!
If you take the quick hitch adapters off that tiller and put the hitch back to its standard configuration it should fit. You may have to alter the PTO shaft length to fit your new tractor properly. Does the 2380 have a category 1 three point hitch?