56 chevy post vin locations??

Recently drug a 56 chevy 2dr post, early 70's gasser, glass tilt front end out of the weeds for a resurrection. IE start the DMV title chase and first thing I need to do is locate the Vin number.
I have looked in the driver door opening/ jams no plates or stamps visable. I have looked at the fire wall, (nope that's been cut out and resized with sheet aluminum for a big block somewhere along the line) and now after hearing there were "hidden numbers" I just cut a hole in the floor under the driver side seat to access top of frame VIN info there, Nada!.
Am I just a dork or is there another spot I don't know about? HELP!!!!!! I'm stuck.

I believe there is also a spot on the top of the frame Left side back by the gas tank.

Thanks for the reply, before I cut another flap in the floor - albeit the trunk this time. :) Do you know other than left side top frame by the gas tank, How far in inches +/- from the rear frame horn that might be. My car has no gas tank and had a fuel cell added in the trunk at some point so I have no tank for reference location and don' know if that was a behind the rear seat tank or below the trunk tank etc.

Any information is much appreciated.
Thanks again.

Taken from the CCI tech manual--Teh vin number is stamped into the drivers side frame rail about 20 inches behind the front left frame outrigger and about 4 inches behind the center left outrigger. Hope this helps. If not PM me and I will try to scan the article and email it to you(if my scanner will work.)