Have you tried
https://pedemann.hpage.de/
Most of what he has is for racing but he does
have some NASCAR stuff.
A few years ago I found a website that had
a lot of paper cars and some NASCAR stuff.
I don't remember the web address, but I
have a model from there... I cant read an
address if there is one. Attached is the instruction
page. maybe some one will see this and can tell you
the website.