If your Fiat 850 has a crispy bottom or there is an unwanted crease in it, you want to restore it so that you are a proud happy driver again. Been there, done that; my 850 was transparent in several places. Fortunately I had an excellent sheet metal worker and access to a professional body workshop so that the entire bodywork could be made like new again. A good dimensions drawing was essential for this. And if it's good, I'll share it:

850 bodemmaten
Again: clicking the image opens a PDF on a new page.