Where are the body numbers on a 66 Barracuda?

So I’ve got a 1966 Formula S here at my shop hidden. A guy stopped in and wants to buy it. It’s a parts car and missing body sections I used for my car. Interior is trashed and drive train is all there. He wants me to “prove” it’s a genuine Formula S. So I show him the vin number, the hood support numbers, put it on the lift and he verified it’s a proper 273 4bbl engine and trans numbers match. But we cannot find the rear body numbers. Under the trunk lid gasket I guess. Before I tear this apart any further for cash- does any one know where I can find a 3rd set of numbers on the car?
I’m lost. I know of only the two I found.
The fender tag is there but the cert card is missing. SN: car is getting locked up now there is Interest in it.
Thanks,
Joe