https://robbreport.com/motors/cars/zagato-resurrects-porsche-356-2748376/
"Porsche cognoscenti will know that there was a special series of Italian-designed, 356-derived vehicles built in the 1960s. Known as Porsche 356 Abarth GTL Coupes, these rarities were, initially, supposed to be a collaboration between the houses of Ugo Zagato and Carlo Abarth, the latter a still-celebrated name in tuning. But for a host of logistical reasons and miscues, that deal fell apart and left only Abarth as a collaborator with the German marque."
This doesn't clear up who designed the body however. I have a 1/24 scale resin body of the Abarth but no glass!!