I think the better question to ask is what backhoe sub-frames (since that is what the backhoe attaches too) are available for what tractor models. Likely a question for a Kubota dealer or may be an email to Kubota.
Do you have an application in mind?
B3030, B3200, and the smaller Grand L's were capable of excepting the BH75 mount but that is all I am aware of.