Nice! Looks like it will work great and easy on and off. Would like a bucket like that on my B2650.
The 4in1 is a factory kubota bucket.
Here in Oz this is standard equipment. Its more unusual to not have a 4in1 which does not seem to be the case elsewhere.
Some pics and the part pate for the bucket are here
http://www.orangetractortalks.com/forums/showthread.php?t=39792
The only changes from factory I have made are a level indicator and bucket hooks.
You can see the indicator in the first pic. Its a simple bit of flat bar bent to vertical and horizontal.
I could not put hooks on top of the bucket due to the cover plate over the hydraulic hard lines. These run over the top of the bucket. Simple solution was to weld them inside the top edge of the bucket