Try getting hold of Bob's aircraft documentation, he has lots of pictures of SNJ's and AT-6's in every color scheme possible. Once you know how detailed a photo pack you need and what type of markings Bob can help you from there.
www.bobsairdoc.com
To get an idea of what is out there look in
www.airliners.net and do a global photo search under "AT-6" and "SNJ" and you can then find something that works for you, then call Bob and find a complete pack that meets your needs.
Land sofly,
Fred Cronenwett