go to this KFOCI linked site to find out more about your car, and to register it/update it (it might already be there!)
http://www.eskimo.com/~hhagen/reg/reg.htmFor 51, the serial number (not VIN) is on the driver's door post between the hinges, and will start 51n-nnnnnn. If it is a 511 it is a Special (lower trim model) and 512 is a Deluxe, or upper trim model. The other numbers after are the serial number of the car in sequence for that model year.
Now, the body tag info on the cowl under the hood has all the interesting info about how the car was built originally. It will start with 51nn-nnnn The 4th digit is the body style and a 2 door in 51 could be a 5110, 5113, 5114, 5120, 5124 or 5127. 0 is for a Traveler (hatchback utility), a 4 is a 2 door sedan, and a 5113 is Special Business Coupe, and a 5127 is a Deluxe Coupe. The other digits are the particular body number that was welded up and waiting to be used...and it can be well out of sequence to the serial # There is also a wealth of other information on this tag ie PNT: Paint Code TRIM: Trim Code DR: Delivery region (1 for US, 2 for export) TR: Transmission code AG: Accessory Group SCH: SCHED(ule) Number ITEM: Item Number. If you can post both sets of information here on the Forum, we can decode it all for you.
cheers! Jim Bartley