Here is the 3d Model I used to print my Rear Diffuser on the back of my 1969 Corvette.
You can see the progress on my Youtube channel.
https://www.youtube.com/watch?v=1Ixm89CGg68

Leave a comment if you do use it!

Measurements may be off, so you will have to resize it correctly before you print.
Take measurements of your car width wise to adjust.

I printed it off in multiple pieces and glued the pieces together.