If I understand correctly, the two main tips that I think might help is to mask a larger graphic to only show within the perimeter of the vehicle outline (minus front
windows and some door handles etc) ...and to give the graphic some transparency to allow a little of the vehicle detail or 3D qualities to show through from the template.
For masking, create a vector path defining the space to be wrapped on the vehicle. If that contour (or compound contour) is on the same layer as a graphic (which would be easiest if the graphic were a flattened rastor image for this process) & then selecting both, you would go to the object menu, choose "clipping mask", and then choose "Make".
Then to add transparency, just select the graphic, pull down the '
windows' menu, choose "show Transparency" and slider the "opacity" slider to whatever looks good.