Just an update. I recieved an adapter from PI Motorsports https://pim.net/ today, 3 weeks after ordering. Price was $135 and I took a few pictures to share with you all. My Pantera is sleeping for the winter so it will be a while before I can get to fitment.
Upon visual inspection the splines look right and the taper is very obvious. The momo with the adapter (left) is a little shorter than oem (right). I think it will be fine.
Now - what about the DeTomaso logo for the center of my new Momo wheel? Any Momo owners want to share their experience here? Thanks, OP