You are right I misread the email from my dealer. I can't use a closed valve system. Thanks for all the other info here I'm going to try and put it to use this weekend.
Have you considered selling/trading the Deere hoe for one that actually fits your tractor? The hydraulic hook up will likely be the easiest part of converting the Deere for your Kubota.
If he's like me go isn't thrilled with the factory kubota BH, building a decent subframe isn't too bad, I ended up just building my own BH that falls in between the kubtoa BH65 and BH77 size and performance wise.