Here's a site I came across:
www.kartonmodellbau.org
It's a German paper building site but it easily translates into English. They have a few superb FREE downloads, mainly ships and buildings, but there are a couple of cars there too. I'm not exactly sure how I found the site, but I might of come across it while exploring the links at Papemau or another similar site.
When I asked @Revell-Fan about it, he mentioned that I could post it as an Internet Find.
Arbeitskreis Geschichte des Kartonmodellbaus (AGK) e.V. - Arbeitskreis Geschichte des Kartonmodellbaus (AGK) e.V.
Arbeitskreis Geschichte des Kartonmodellbaus (AGK) e.V. - A German association that researches the history of card modeling including publishers, designers and authors and the cultural and economic historical context. It also provides a database of card models and catalogues.

It's a German paper building site but it easily translates into English. They have a few superb FREE downloads, mainly ships and buildings, but there are a couple of cars there too. I'm not exactly sure how I found the site, but I might of come across it while exploring the links at Papemau or another similar site.
When I asked @Revell-Fan about it, he mentioned that I could post it as an Internet Find.