The paint code 171 on your data tag should be followed by a G (Glasurit) or H (Heberts).
The PPG paint system should be able to match 171 just by the paint code. If they have any issues, go elsewhere!
If you have having a full body paint job done, it is less of an issue that refinishing part of the car, where the color match would have to take into account color fade/change from time and exposure.