Hi Andrew,
Thanks! I can't comment on the dimensions of a <gasp> Kabota backhoe at this time, but Richard at Brotek certainly could. I recommend getting in touch with him to ask about the differences. It's been a little while now, but I think the only changes I had to make was to get some shorter bolts, cut down a shaft, and mill down the bushings on the thumb itself. Last, I had to drill some new 1/2" holes on the thumb mounting sideplates. Everything else I did was fluff, I believe.
I'd bet Richard would be happy to adapt his 260 thumb for your 46. I'm sure he'd like to be able to add to his product line. I've been meaning to let him know about this adaptation, but haven't had the time to do it thoroughly.
Regarding hooks for your bucket, those in my photos are ones I welded onto that old bucket long ago. If I could do it all over again, I'd get Ken's Bolt On Hooks (scroll up for link).
How do you like your 46 hoe?