I do not feel confident to ID the pre-54 Suburban interior colors. The colors in your photos sure do look nice. The darker color seems very metallic. From whom did you get those sample colors?
I think that the darker brown is similar to the brown used in some 54/55 GMC trucks (but I am not sure). My 54/55 GMC COE has that dark brown. The PPG Prophet computer analysis showed it to be metallic (I could not see that with my old eyes).
Do you have a friendly PPG dealer nearby? They might be able to match the old codes and even spray a few samples?