28 Canadian Roadster questions

[chrs1961815]

I checked the engine serial number on my 28 roadster and it is a canadian built 1931 engine which should not be in the car but that is besides the point. My car was advertised as a 28 Roadster but the wheels are a 1930-31 type and the windshield post has mirrors on the post instead of on the wings. Also, when I bought the car, somebody had a 1930 model a plate holder on it. Is there anyway for me to tell if the car is actually a 28? Frame numbers or body numbers?