Just remember that you are looking at trucks that are 70 plus years old and regardless of how close (or far) from the orginal any individual truck may be they are not really comparable to modern trucks in terms of both operation and maintenance.
I am not an expert on model designations but a 3800 is going to be a pretty heavy duty version that is going to be a lot more truck like than the typical 3100 models that are a lot more common.
My truck is a 1950 3600 version and it has signifcant differences from the typical 3100 versions most people talk about.
