I'm making a custom case for the Raspberry Pi and need a CAD model that is accurate to work with.
I've seen a few of them on GrabCAD, but I'm uncertain if those are good enough. Are there no official CAD files of the Raspberry Pi?
If you look on the Raspberry Pi Wiki Resources, under Documentation you will find 3D CAD files:
RPi Model B 3D CAD files
Theses are various 3D CAD Versions in both RAR and ZIP.
I would say those are the "official" 3D CAD files. You can cross reference some of the dimensions from the Raspberry Pi's FAQ:
What are the dimensions of the Raspberry Pi?
The Raspberry Pi measures 85.60mm x 56mm x 21mm, with a little overlap for the SD card and connectors which project over the edges. It weighs 45g.
There are CAD Models on Grabcad that are made around the official documentation: