neighbor brought it over to have head gasket changed. but, the head had several cracks, so I got a reconditioned head and a gasket set. The bores do not look bad.
Like GeoHorn said, did you checked the block for flatness as a very overheated engine can distort the block.
But even with that the chances of getting coolant in the oil is very rare.
Now why did it overheat? One possibility could be that there is a freeze plug under the front gear case and that could have rotted out or popped out from a freeze condition and that is why you're getting coolant in the oil.
There is very little chance of anything else causing the issue as Kubota blocks have very little possibility for a cracked block.
One far fetched possibility is someone has changed a freeze plug or more commonly installed a block heater and drilled through the block when doing so.