What I always do is...
1- save each view as a separate image, and trim off the white areas
2- rotate the views slightly (in photoshop) so they are properly aligned
3- take the official dimensions, then resample the images at a scale of 1" to 1 pixel so they are scaled properly to each other
4- then correct the drawings due to photo evidence
Like the posters above, it needs to be said that three view drawings should only be a starting point and a guideline. The most time consuming part of design work (other than making instructions) is just doing the research. I often collect over a thousand photos, drawings, flight manuals, etc for over a year before I even attempt a design effort. It's made all the harder when there are no more examples of these airframes in existence.