Hi Zen,
follow this link:
http://www.blueprint69.com/
Although the prints are not cheap, I think this is what you are looking for.
Further I think there were some Tipo 33 blueprints published in an issue of "Style Auto", but I remember that these showed a Spider.
Another source for Tipo 33 drawings is the book "60 vetture ai raggi X". There are drawings of a Tipo 33 Prototipo Sport, engine and body.
Buying the blueprints will be cheaper anyway, because the other publications are out-of-print and not easy to find.
With best wishes
Ciao Carlo
