We have cleaned off the top of the frame from the firewall up to near the radiator--driver's side. Nothing. Same thing on the passenger side. Still nothing.
What are we missing?
You will find the serial number on top of the frame rail on the passenger side between the firewall and the motor mount - likely adjacent to the starter. If there is a lot of rust on the top of the rail or the area has been refinished, the number may be faint. Please keep looking! If you have the original engine, the same number will be found on the engine block just above the water pump.
I'm at work currently but can post a photo from the shop manual which shows the two locations this evening.
Hope this helps you.
As promised, here is the photo from the 1942 shop manual showing the two locations of your car's serial number. I added the color to the arrows to make them stand out.