You can use the Motor Application Chart to see what motors were available on any W-body car. Just locate the car of your choice on the left-hand column and the car's model year on the top row. Where the row and column intersects is a list of VIN numbers which correspond to the possible motors that were available in your car. You can then locate the appropriate motor on the VIN Key Chart. This chart does not take trim lines into account (i.e. the chart would not differentiate between a base-model Pontiac Grand Prix and a fully-loaded Grand Prix GTP).

The engine VIN code is the 8th digit of the VIN!