All the VIN will tell you is the model year, 1973. To determine if it is matching numbers, VIN, engine and transaxle that it was built with, in the distant past, you could get a COA, Certificate of Authenticity, from PCNA. Although they often had errors in them, it was a starting point. Nowadays, Porsche offers another document for a lot of money, where you provide your engine number, etc., and they will tell you if it is the correct engine...
Might be better off doing a Google search on your VIN or going over to 914World.com and checking their VIN registration section to see if your car is already listed in their data base.
http://www.914world.com/bbs2/index.php?act=membervins&byYear=1973 I believe you may need to join the site to get to that search. Good luck in your search. A '73 is a great year for a 914.
