I am assuming that these drawings aren't available to the G.P? And what about locos 1 + 2?
Ben, in the book you should be receiving soon, there are side-view drawings of engines 1 - 4. These were based on Disney painting diagrams, so they aren't really true blueprints. Preston Nirattisai, the (then) civil engineer who did the drawings under my supervision, used a CAD program. We had some known dimensions, and we used those where we could. The rest of the drawings were made using detailed photos of each engine, and keeping all details in proportion. They are not 100% accurate, but they are very close--so close that people in Imagineering refer to them often, and have used them to create some of their pins.
As for engine No. 5, the Ward Kimball, we did have access to some of the blueprints, which led to more-accurate wheels and other details. However, we used the drawings of No. 3, basically from the running boards down, as the basis of the Kimball, since they're the exact same class of engine, with the same dimensions. We changed the details accordingly to match.
I do have several dozen drawings of the Fred Gurley, including the cab, frame, tender, and rear truck. These are being used by N.Parrot for his model. I've sent copies to Preston, so he will be preparing ultra-accurate drawings of this engine if and when we ever get around to doing a second edition of Welcome Aboard the DRR.
(I've also posted some of those drawings over in the Drawings Forum. You should check it out sometime!)