I believe that an article was published at one time in the modelling press concerning the use of Ratio MR suburban coaches as a basis for GER coaches.
I do not know how close a match this enabled the author to achieve, but I can see how these kits could be adapted to form GE 6-wheelers. The panelling style seems reasonably close to some GE 6-wheel coaches from the 1890s.
Guy Rixon of this parish has hopes of producing 3D printed GE 6-wheel coach accessories - axle box/spring assy, roof