There are usually discrepancies in raw scanned data especially when using non-contact scanning such as with lasers or LEDs. Variances can occur for many reasons, reflections, shadows, etc… Keep in mind that this part has a textured finish which can also affect the results and it is a 30+ year old slush casting that may actually have some of the distortions pictured.
Normally scanned data is brought into another software package to be post processed into a usable part. The most common is Geomagic. The 3D models posted are an interpretation of the scanned points using prismatic elements such as planar and cylindrical faces, and symmetry was enforced where it can be assumed to be the original design intent.
The model in the stl file cannot be printed as is in that it has zero thickness. Some 3D printers have software that can thicken the model on the fly.
The 3D models in the STEP and DWG formats can be exported from most CAD software as an STL file for 3D printing. Depending on the type of 3D printer you may need to add extra support structured for the more delicate features.