I can’t help with any answers to the question but if you go to Kubota illustrated parts list here
- K-PAD - Parts Lists - Illustrated Parts Lists - diagrams
apps.kubotausa.com
Agree to the terms and search for your tractor model, there will be something that says OPTIONS. There will be a listing of the optional implements that fit the tractor. You may have to find the L2900 tractor and identify the backhoe that is available. Then find the illustration that shows the subframe or its components that attach to the frame. Write down the part number.
I think there is a way to search that same Kubota site for that part number and find the tractor models it fits. I know that on the Messicks site you can find that part number and a list of compatible models.
That may help.