I am building a database to track and display (web, intranet) a truck
dealer's vehicle inventory. I'm running into difficulties in designing
the structure of the tables to hold the truck information.

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,
make, model, engine, transmission, wheelbase, gvw, and on and on and
ON.

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.

And I could separate the attributes into separate tables depending on
the product type, but then I'm stuck with ugly one-to-one
relationships. I'm not sure where to go from here. Any help would be
greatly appreciated!!!