I've got a 60" King Kutter BB that I use behind my B2400 (24hp). I believe the manual calls for 54" max behind this unit also. I can tell you that the tractor strains using this size blade as low range is mandatory and with the rippers at full depth, it doesn't take much to stop it in it's tracks! The bright side is that my Kubota seems to pull it better than my Father-in-Laws brand new 4115 Deere! /forums/images/graemlins/grin.gif All said I think if you can find a reasonably priced 54" BB you'll be happier than with the 60" unit as far as tractor performance.
I was looking at the KK 60" blade. They also sell a 48" blade but I'm not sure if it will cover the rear tires. I have not scene too many 54" blades. I need to do some "light" grading behind the barn. If it takes more passes, so be it, it more seat time.
I use a 48 inch on my 2410 and it works great and it does cover the tracks with the wheels in the standard position. I would not get a 60 for that size tractor except for use as a grader--maybe. J