Pontiac chieftain help

Hey all, I have a 1951 Pontiac chieftain and I'm trying to get a title made. As of now the only hold up appears to be locating the ID number off the frame, but I have not been able to find it yet?
The detective helping me said it's between the frame and body on the driver side near the rear of the transmission according to what he has been able to find. There's a lot of dirt and surface rust that I'm cleaning away, but haven't had any luck.
If anyone knows exactly where it is, pics would really help in this situation, or more info to the location, I would greatly appreciate any help at all!!
Thanks,
Pete

 

Don't know about a serial # on the frame but my '50 Four-Door had a serial # on the driver's windshield post, about half-way up, spot welded on.

 

The mysterious "frame serial number" I've looked for these on every car I've owned, restored or cut up. I've never found one. I think it's a myth.

 

Haha. Thanks for the replies. I have the one on the driver A pillar and the body info on the firewall. I don't have the original motor so that's where the title creating topic comes in without an existing title. I gotta at least try by cleaning the frame off and the detective will look one more time as well. We're just hoping the DMV doesn't give me any trouble

 

I found it this morning! On top of the frame-driver's side-outside rail-even with the tail housing of the transmission. Took me around 5.5hrs total, but I found it!
A couple of the digits are faint but it matches the vin number.
Thanks again for the responses!
Pete