I had forgotten but I had in fact replaced a full set of SPD-SL cleat nuts with claw-nuts in the past

Carbon Sole Repair with Claw-Nuts by
Timothy Takemoto, on Flickr
so to convert a mountain bike shoe to a road bike shoe, all I would need is a template to position the three holes. Since the cleats themselves allow for some adjustment, this need not be all that exact, imho.
Claw nuts can be purchased cheaply here (M5 I am pretty sure)
https://www.aliexpress.com/item/32898135040.html
Should anyone be interested, my thoughts on old threads are explained in my "About me."