So what was Nardi's role in Lancia's early Aurelia competition cars?
Nardi had been a friend of the family (primarily of Giovanni Lancia's son Massimo) in 1930, and knew the Lancia cars well. They were going to go to Modena to work at Maserati, but Massimo's untimely death in an airplane crash in 1932 put an end to those plans. Nardi went anyway and became Ferrari's driver, and worked with him for many years, into the 1940s.
At that point, he returned to Torino, and started making his own particular cars and products, including twin carb kits for Areas and Aprilias. His shop was located close to Lancia (I believe across a courtyard) and in the early days of the Aurelia, he provided tune-up services for the factory and later for privateers.
First off was a double carb kit for the B10, then another for the B20 s.1, used in the Mille Miglia of 1951. Two further kits were made, one for the B20 s.2 (same carb, different manifolds, as Lancia had changed the heads), and the 6 carb dell'Orto solution (done in two versions).
Of interest is the evolution in these early years at Lancia, where initially the expertise comes from Nardi, and then quickly (starting end of 1951 and into 1952) Lancia gets more seriously interested in racing and engine development, and takes over the tuning of their cars. The high point here is De Virgilio's design for a four carb setup (single Webers) used in the s.2 Corsas. This kit may well have been cast by Nardi, and it showed up in his 1952 F2 car, powered by an Aurelia engine, supposedly to the disgruntlement of Gianni Lancia, who did not like factory developments showing up on someone else's cars.
Nardi continued to make further kits for the Aurelia, most notably the one for the 2.5 liter engines, used in B20 series 3 to 6, and would also be fitted to some B24s. The relationship between Nardi and the factory remained close - there is one example (I think either s.3 or s.4 B20 motor) that is taken out of a new car, refitted by Nardi with his hot cam and twin carb setup, and then tested at Lancia and then refitted to the car. Not sure who was responsible for what in that interchange, but the customer was likely very happy to have this all done for him.
In each of the Aurelia heads, manifold passages are changed to improve breathing, and these required different setups from Nardi - the number boggles the mind. There were six different heads, and the number of combinations of heads, valves, cam and carburetor are somewhat bewildering (ref: pg. 295 in the book, shown below).
Nardi was assisted by Gaudenzio Verga, likely designging the breathing enhancements. Verga was an old Lancia hand, coming to Lancia in 192. Prior to that he had been at Chiribiri in Torino, making 4 cylinder race cars from about 1910 to 1927, then joined Lancia and was with them into the 1940s, before migrating to Nardi.
For more detail, see Lancia and De Virgilio, At the Center (pg. 99 and following).