As Stanglover Said, Once the underlayment tar permeates the buildsheet paper there is not much you can do. The tar just dissolves everything over time. I tried different light spectrums, scanning and digitizing it, and then magnification. It helped in some places where the tar damage was light, but not much success. I had the car's original invoice and fortunately, I found many of the original paint marks. Along with the bits and pieces I could extract from my car's buildsheet and looking at as many other build-sheets with similar options and build dates as close to mine as I could find posted online, I was able to fill in almost all of the blanks, with the exception of a few, including the rotation #, which is unique to each car.
I then decided to recreate my car's build sheet the best I could. Using a windows font development program, I designed the characters (Size, Shape, Spacing, color, and fuzzy appearance) to match the ones used by Ford. I can now type the buildsheet up in MS word using my custom font, and the buildsheet image as a word document form in the background and then print it on my HP Deskjet printer using thin legal size paper. I then trim it to buildsheet size, fix the inkjet ink to prevent the ink from running from water damage, I use my made in china handy dandy ring binder 18 hole punch (need 20 holes on each side). Finally with the ink fixed and holes punched, I then lay the buildsheet flat in a cookie baking sheet with a 1/2"+- of black tea water for about 1-2 minutes to create the discoloring and staining. I dump the water and place the buildsheet in the oven on the lowest setting to dry it as fast as possible without heat damage. It was a good amount of work, but in the end, it was worth it. A least it was for me anyway.