68 Barracuda trunk/quarter panel transplant?

Oh Boy! I lost track of your other thread, but I thought the intention of finding another shell was to find one to build instead of the black one? You have tripled the amount of time that it's going to take. Now you have 2 cars to dismantle and one to build, and it takes considerably more time to take it apart where you can reuse the parts. There's not really enough pictures to really say, but the donor might be the better option to build.

You have the enthusiasm, but you need a plan. I couldn't really recommend to a novice to clip a car. More to then stitching it together and it's not a learn to weld project. Too many horror stories of clipped cars scattering the occupants and generally a frowned upon method these days.
The donor has a rusted out floor pan, but in general seemingly better metal. It looked a lot better before I cleaned it out, there was a lot of dirt hiding holes in the donor pans. Beyond the floor pan the rear drivers side post where the roof connects to the body that's got a fair bit of rust too.

Unfortunately it doesn't seem I'm very good at finding cars. :(