FSX/P3D. To be rather honest, I am not much of a fan of old stringbags. Alabeo's Waco is one of my favs but that is just a modern aircraft that looks old. GoldenAge Simulations specializes in developing the truly older generation line of aircraft. I don't own anything they have released but the upcoming Davis D-1 project looks a bit appetizing to me. Indeed I think I will have to get my hands on this one. More about GoldenAge via the source link below.