How does one determine what type of body they have for a 1964 Oldsmobile 98 4 door hardtop?

 

The four door hardtop (bodystyle 3839) is called Holiday Sports Sedan. It has door windows only, no post between the side windows and large blind sail panels.

A Town Sedan (bodystyle 3819) has full-framed windows and a small triangular window aft of the rear doors. It is often called a six-window sedan. 1964 was last year for this bodystyle at Oldsmobile.

A Luxury Sedan (bodystyle 3829) shares the Town Sedan's six-window styling, but has frameless door windows and no post.

 

when does the Holiday, W4, and W6 come into play as that is what is listed in the kelly blue Book

 

See above. Holiday is Holiday Sports Sedan. I have no idea what KBB is talking about with W4 or W6 since it doesn't match any factory or Fisher Body nomenclature. I would assume W6 might be the six-window sedan. Oldsmobile itself used the W prefix to ID high-performance options, and that started in 1965.

Are you trying to ballpark a value, or trying to identify a car you own or are thinking of buying?