Guys, guys, guys. Revell, and Aurora were the companies with the multi-piece bodies; top, sides, front and back. Their lines of sports cars, especially Revells, can still be found on E-bay. Revell had the Porsche 356, 1959 Corvette, Mercedes 190SL, and Austin-Healey 3000. The kits were 1/25th scale and were released in both street and competition versions. Aurora had a line of 1/32nd cars, Cunningham, Austin-Healey, Mercedes 300SL, Ferrari, Triumph TR-3, and maybe Jaguar XK-120. At least some of these kits also came in two versions: street and custom.
Jo-Han, Monogram, SMP, and AMT, amongst others, had essentially one-piece bodies