There are often questions about how to properly identify the 1932, 1933, and 1934 Model B, BB, and Model 46 Truck cabs. The cabs were similar but different each year. The major noticeable differences relate primarily to firewalls, back panels, and fuel tanks.
Pictured above is the 1932 Model B and BB truck cab. The most distinguishing feature of this cab is that it used the same separate firewall as the Model B cars. The separate 1932 firewall design shown above was not used on the subsequent 1933-34 truck cabs.
Pictured above is the 1933 and 1934 style Model BB and Model 46 cab with the integral welded firewall. This firewall is not removable, and is unique to truck cabs. It has a generally similar appearance to the 1930-31 Model A/AA firewall. There are differences in fuel tank placement and mounting as well between Model 46 and BB.
The pic above shows the back panel of a 1932 cab, which was also similar to that of the 1933, but not to the 1934 cab. Contrast the pic above with the following pic of a 1934 back panel.
For 1934, Ford added a wide reveal molding shape above the previous molding features in the back panel stamping, as shown above. It is located immediately below the rear window reveal features. This was added to further stiffen and strengthen the back panel and reduce noise and drumming.