The Kubota engine plate arrived today. the box was completely destroyed and taped up - the only thing in it was the thing that counted, the plate!
I went out to the garage and did some comparing and took a few rudimentary measurements and started planning the process for making the adapter.
Here's the scene of the crime:
The plate mounts up just fine to the D1005. The eBay listing said it was from a V1505, or some such, and I gambled that the "05 series" engines would share the bolt pattern. The locating pin mates properly.
The center of the input shaft is drilled out from the Suzuki or Aisin or wherever facory. I suspect it is metric but a 5/16" transfer punch (from Harbor Freight, so it's probably metric anyway) went about 3 inches into the hole and was a snug fit. I'll be using it to mark the center of the adapter.
It will look something like this when it's done. I will be leaving the bottom sliver of the transmission bellhousing open, not making a full plate, so that I can have access to the torque converter bolts - similar to the original opening.