The serial number, which may or may not be the VIN, it depends on how your state titles is here. Located about 5" above the lower DS hinge opening. For a 1949 this number will appear nowhere else on the vehicle, the frame is not stamped.
https://www.flickr.com/photos/advance-design_parts_co/8130452603/in/album-72157631870734114/
https://www.flickr.com/photos/advance-design_parts_co/17057160050/in/album-72157651722976780/
The second photo also clearly shows the unique clutch head attachment screws for this plate. The plate as shown is exactly what you should find for your truck. Some states title to the engine number, other states like Utah titled to both back in the day.
https://www.flickr.com/photos/advance-design_parts_co/9035376513/in/album-72157631867396207/