Hi and welcome to the mad house
If going the book / saturn way then you need to use the book and the Saturn together along with the list of corrections.
Alternatively speak to Phil at talon motorsport as he uses a new diff case to mount as per the sierra build , it replaces the long diff arms, I hard mounted my diff with the long arms just replaced the rubber mounts with solid.
Read any of the build threads and pick ideas , pitfalls etc from those, feel free to look over my build photos.
Don't forget we have all made mistakes and had problems so don't be afraid to ask any questions no matter how small.
Good luck, Gary