Christpher,
There are a number of options, in a variety of price ranges. Look for books by Ronnie Spain and John Allen, and then there is the SAAC Registry...lots of info, and a registry of known previous and current owners.
Other great reads, not entirely GT40 related or technical, are the books by John Horsman "Racing in the rain." and A.J Baime's "Go like hell" .
I'm sure that there are many others, those are just some that I have experience with, and enjoyed. My SAAC registry is already on its last legs.
As for origianl drawings, there are bits and pieces, but nowhere near a complete set readily available to the general public. There are a few complete sets of technical drawings around, some original and some reverse engineered. You may be able to obtain a set, but only after finding and killing the owner. I think obtaining the Holy Grail would be easier.
Good luck, and happy huntin.