[Specialk]

At Shelby, we didn't put anything between the 3/4" tubes and the body. We just riveted the body to the tubes.

If you are using the fiberglass trunk tray like the 4000 cars, it is shaped like the SC aluminum trunk. There should be piece of aluminum like in the photo below. That piece gets sandwiched between the body and the 3/4" square body support tube, with rivets going through the body, aluminum panel and 3/4" square tube. Then rivet the aluminum panel to the vertical flange on the trunk tray.

Shelby uses a piece of channel shaped rubber at between the tray and body. It should all fit tight and make a weathertight seal.