Carl's "differentiations" are excellent.

Here are some more early 1949 vs late 1949 features (much of the information provided by Jim Carter).

Here are 1950 features (again, much of the information provided by Jim Carter).

Here is another excellent article that describes 1949 and 1950 differences.

Tim
1954Advance-Design.com
1954 3106 Carryall Suburban
1954 3104 5-window pickup w/Hydra-Matic
The 216 and early 235 engines are not "splash oilers" -- this is a splash oiler.