In the car.str file way down towards the bottom it looks like this:
[numbers]
num = 3
pos 0 = {202,7}
height 0 = 27
orientation 0 = 3
pos 1 = {149,141}
height 1 = 32
orientation 1 = 0
pos 2 = {92,206}
height 2 = 32
orientation 2 = 0
You can change where the number shows, which direction it faces and how big it is. These are off one of the SDC Big Blocks I made so to get an idea on placement open up a modified skin and find where those coordinates come out to on the template.