Pop the trunk look at the sticker with all the alphanumeric codes and compare them to the codes listed here This will give you some good insight. http://www.nastyz28.com/rpomenu.html
or just take it to the dealer and ask them for a copy of the vehicle manifest, that will tell you everything that your car has/had when it rolled off the assembly line. don't know if it costs anything or not, probably does
Herc, a lot of my codes aren't listed on that site, and those that are listed don't seem to actually coincide with what my car has... According to one, I should have a 5.0L V8.