whats the first number of your Vin. if it is a 3 then your car is just a very early 73. i'm not totally sure though also, whats the unit number in the vin?
I would think any car built after Sept 1972 would be a 1973 Model year car ... Next model year vehicles always come out in the AUG/SEP/OCT time frame .... A 12/72 built car is definitely a 1973 ...