I'm needing to replace one of the trunk floor extensions in my 65 Coronet. I thought the extensions were a separate part from trunk pan. Is this right? If so, where is the seam located where the extension meets the trunk pan?

I've got a couple of extensions that were cut out of a donor car. They were cut about 7 inches in from the edge of the trunk floor. I was thinking there would be a seam so I could drill out the spot welds, but on quick inspection I don't see a seam. I haven't sanded the surface yet to see if it would expose any spot welds.

I didn't think the trunk pan and extensions were one piece. If it is one piece, how are you guys replacing just the extensions? I need to replace the extension including the top edge of the pan where the trunk pan folds down and extends to the bottom of the quarter.

Thanks!