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Oh the mind boggles...Not a lot out there. I've got one manual. I think it's an erection manual, but a poor copy, and all the microfilmed drawings for it.
I had the thought that rebuilding a BT-13 into a P-66 replica powered by R-1340 would be neat. My father saw a BT-15 in Tulsa about 1950 that had flush riveted wings so you just need to find where those went(probably into the aluminum Coke cans at the supermarket).A couple of us were looking at build several of them a bunch of years back. There were enough specialty extrusions required, it was going to be hugely expensive, so the idea got dropped.
There's a lot of times when flying a T-6 that you realize even though it's fighter-like it needs more power to be a fighter. A BT-13 modified to look like a P-66 with retracting gear and shorter wings would be a lot lighter than a real P-66 and probably slightly better than a T-6 as that T-6 canopy has DRAG written all over it.The original design work on the P-66 was going to use as much commonality between the BT-13/15 as possible. But by the time the a/c went into production, there wasn't much left structures wise that was common between them. Some of the fuselage furnishings were common, but few other items.
Bob: Using a 1340 would only give you half the horsepower that the -66 had. Would make for a very anemic performing a/c.
Search for "Did Northrop and Vought help design The Zero?"link please for the article on the issue of the possible impact of the P-66 design on the A6M2?