There are two Vals (including an engine now) at the Pearl Harbor Aviation Museum and another (and a tail section of a fourth I think) at the Nimitz Museum in Texas.
I would LOVE to crawl inside them to start scanning parts but I don't have the connections. I'm just some schmoe at this point!
There are also these original documents in the collection of the National Institute of Defense Studies in Tokyo, but I wouldn't have the slightest idea of how to get access to them:
View attachment 822460
ALSO, Smith's tome claims that the chief designer of the Val gave Bob Diemert copies of the original blueprints for his work, but he might have been conflating that with Jiro Horikoshi sending him blueprints for the Zero. I'm trying to hunt down those Val blueprints too.