Chassis, engine, tuner, body, assembler>
One thing that wasn't mentioned is that many cars were built "to the order" of the owner. There were all kinds of cars that were "ordered" by a particular person.
An assembler company (such as Tinarelli) would buld a car for a certain person. A good example would be a car built for Bottazi, who was a member of the Scuderia Ambrosiana. The assembler was Tinarelli. The bottom end of the motor was Fiat. The cylinder head was designed by Roselli, who was an Alfa engineer involved with the Bimotore, than later, teamed up with Giusti to form a company called GR, that was also known as Casa 'dell Auto. (The company also made various parts and were involved in the construction of the Testadoro cars)The chassis of the car was by Gilco, and the coachwork by Colli. The final tuning was done by Volpini.
Should we really have some type of formula as to how "hot rods" like this, and even America "specials" should be called? Personally, I think we do, as without some set of rules as to naming these kinds of cars (and there are hundreds, if not thousands), it gets very confusing...
or is it good enough just to call these "Fiat specials"?