Let's see now:
If the engine is the original engine that was put into the chassis of this car when it came down the assembly line and if the engine is not a restamp, then it was stamped at Dearborn on May 26, 1931 but it does not tell you when the car was built. To see if it is the original engine number, you will have to remove the body and view the stamping on the frame if still ledgable.
Next, does it have an assembly code? Go here to review just where you may find the assembly code on your body:
http://www.plucks329s.org/pdf/studie...ND%20CODES.pdf
Your car has no indenteded firewall...this appeared in May 1931 so my gues yours would maybe be an early May 1931 or earlier right before the indented firewall came into the picture.
You can also purchase the MARC/MAFCA Restoration Guidelines and Judging Standards which will help you key ou the rest of the car to try to determine an aprox. build date.
Looks like it will be a nice restoration...just do not get discouraged!
There is a start for your history.
Pluck