VIN# should be on the fender tag (inner fender next to battery), trunk gutter (driver side under weatherstripping), Radiator support (top rail), motor (pad just above oil pan), transmission pad, and build sheet (if you're lucky enough to have one).
Numbers matching means different things to different people. Some folks think numbers matching means the original drivetrain is still in the car. Others think that EVERY part has the correct date code- carb, distributor, alternator, starter, plug wires, rims, radiator-EVERY part on the car being correct for the build date of the car.
Obviously the latter requires much more research and is a very difficult goal to attain.