Who knows all those race cars?
Finally this one is solved!
Car A: solved by pnegyesi: Alfred Fegers' AF special, driven by Paul Dübbers
Car B: solved by pnegyesi: Hinz VW-Spezialintertyp
Car C: solved by Wendax: Alpers Eigenbau special, driven by Karl Golka
Car D: solved by Wendax: Baxmann Fiat 1100ccm