You don't ask any questions, so perhaps general observations are appropriate. Your choice of IC, the 2917 looks very good. Of course, you can expect to hear suggestions from other posters that this can be built with a small PIC or AVR chip instead, which is true, but that would be more work for little gain. Anyways, the application problems include how you will interface your vehicle to this chip and how you want the output to behave. You need to decide how many LEDs you want to come on as this will determine your current requirement at the output and thus answer the question of whether you need an external relay/transistor or not. As for the input, I see there are a few application examples in the data sheet and app note, so just pick the one that matches your plan and copy it. To make the shift point adjustable, you will need to use a variable resistor for R.
As mentioned in that one referenced thread, make sure you use a good input voltage filter on your 12V power supply from the vehicle. I often suggest that you can't really go too far with this, even to consider adding an additional linear voltage regulator and some additional RC filtering.