It would be nice if one of the fabricators out there would get serious and do an Aurelia Zagato, as it once was. That would be a welcome addition.....
On another note, the 2 liter motors David refers to really do have their own charm. They spin much easier, smoother, and generate significantly less heat. Just a nice motor. Not as sure about the 1.8 motors, they might just be a bit too small....
On the subject of specials.... one of the most interesting ones I ever saw was the original prototype 538 motor (1.569, c. 1946) put into an Aprilia sedan as was done by the factory some 60+ years earlier. It was surprisingly charming - had lots of torque and was very smooth. I keep dreaming (encouraging?) a run of 20 specials like that for sale.... but it won't ever happen, sadly.
That would be neat to have....