Truck Dealer Database

Brief Description:
There are different types of products that they sell: Buses, Heavy Trucks, Medium Duty Trucks, Light Trucks, even Trailers. Each individual vehicle/unit has a Dealer-assigned Stock # (never a duplicate).

Each individual vehicle/unit is either New or Used.
Each individual vehicle/unit has a Factory-assigned Serial #.
Eavh individual vehicle/unit has a number of attributes, ie: year,

Difficulty #1: Different product units have different attribute types. --- The different units carry different attributes important to someone wanting to know about that type of unit. For instance, a light truck has what is called a trim. A heavy truck does not have that. A heavy truck has a cab-to-axle measurement that a trailer does not have. And so on.

Difficulty #2: Trucks are HIGHLY customizable. --- Although there are duplications of the same vehicle where all of the attributes are exactly the same, it's somewhat rare that the dealer has those in inventory. They may have 20 2005 Ford F150s, but stock # 12345 might be different in color, while stock # 12346 is different in color and has a different engine spec.

Any suggestions as to how to setup the table(s) for this? I could have one table with the Stock # as the Primary Key, but I would have multiple attribute fields as either NULL or redundant. For instance:

Stock# Serial# Type Year Make Model Color Fuel Trim Tran 12345 A53234 LT 2006 Ford F150 Green Gas XL Auto 12346 A83493 LT 2006 Ford F150 Green Dies XLT Auto 12347 A53d34 LT 2006 Ford F150 Blue Gas XL Auto 12348 A8da93 LT 2006 Ford F150 Green Gas XL Man

12349   A8d092   HT    2003  Ster  AT75   White  Dies        Man
12350   Ad3921   HT    2004  Ster  AT75   White  Dies        Man
12351   A499d3   HT    2004  STER  AT85   White  Dies        Man
12352            TR          J-CR  PUP    Blue
12353   dfdfdd   TR          J-CR  PUP    Green

Keep in mind the number of attributes is far beyond that shown above.