Not sure if this is the Tondelli car but certainly could be
http://www.targaflorio.info/nesti.htm
I wondered if this was my car originally but looking at this photo it looks more like a B23. The roll hoop construction has the bracing from the rear as per B23 whereas B31 is braced from the front. Shame because adding Targa to my car would have been good, but this evidence clearly says not.
There are a few other photos of Nesti on the Targa in 77 if you search for them.
Doug