I know the answer for these 11 cars. Consider the year as indicative.
1arb: Alfa Romeo Sprint Barchetta 2500 CM 1955
5arb: Alfa Romeo C52 3000 MM recreation owned by Al Cortes
9arb: Alfa Romeo 1900 Barchetta Sportiva 1955
10arb: Alfa Romeo 1900 'Conrero' Evocation
11arb: Alfa Romeo 1900 SS Barchetta Conrero 1955
15arb: Alfa Romeo 1900SS Barchetta Stradale 1954
16arb: Alfa 1900 Barchetta with 2.4L Alfa Engine 1963
18arb: Alfa Romeo 1900 Barchetta 1953 from Argentina
22arb: Alfa Romeo 6C 3000 PR 1953
36arb: Fiat 500 C Barchetta
40arb: Alfa Romeo 1900 Barchetta Sport 1954
I do not have a definitive proof for these 10 cars. If anyone will find the solution, it will be worth a point (and not 1/4 of it), if no solution will arrive in a reasonable time, points will be awarded to the puzzler who find the name as it is known. The year is indicative.
7arb: Alfa Romeo 6C 3000 Spider Who built it? If no name is found, it goes to oko94.
13arb: Alfa Romeo Disco Volante Fianchi Stretti recreation 1952 Who built it? If no name is found, it goes to Carnut.
14arb: Alfa Romeo 6c 2500 Barchetta Evocation Who built it? If no name is found, it goes to oko94
17arb: Alfa Romeo 1900 Barchetta Conrero Who built it? If no name is found, it goes to Carnut.
21arb: Alfa RomeoDisco Volante recreation from California Who built it? If no name is found, it goes to Wendax
25arb: Alfa Romeo 1900 Barchetta Frianchistretti Replica Who built it? If no name is found, it goes to Wendax
26arb: Alfa Romeo 1800 Barchetta 1953 from Jakarta Who built it? If no name is found, it goes to pnegyesi
27arb: Alfa Romeo 1900 SS Barchetta Who built it? If no name is found, it goes to Carnut.
35arb: Alfa Romeo Disco Volante recreation from Georgia Who built it? If no name is found, it goes to Wendax
39arb: Alfa Romeo Disco Volante replica (Tom Zat's) Who built it? If no name is found, it goes to oko94