It's not enough to download and decompress to the right Class folder. You have to install to the correct folder holding that exact type of car. In this case, the Ford GT40 folder.
And don't take this in the wrong way, but you are installing the above GT40 car in GT Legends?
I install cars a bit differently, I've found, than a lot of people. What I do is to extract the file inside a desktop folder, then investigate what files are there. In particular, some cars come in a Game Data folder, with others 'tucked inside'. All I want is the last folder holding loose files pertaining to the car in question. When I find that folder, it's generally a two or 3-digit numbered one, (referencing the car number) and I copy and paste it into the correct car folder.
A bit wordy, but hope it helps...