The 2004 Dura-Ace hub has an aluminum Freehub body, so it only works with 10 speed cassettes.
Dura-Ace 10 cassettes have titanium sprockets from 18 teeth and larger.
10-speed cassettes have a recess built into the back of the big spider module, allowing them to fit farther onto the Freehub body than older cassettes. This limits the possiblities of customizing the ratios, because you can't install a flat sprocket behind the spider module...you run out of clearance at the other end if you try.
Do you want a cassette combination Shimano doesn't make? We carry many individual sprockets for Shimano cassettes, and can provide most sizes. The most economical approach to custom cassettes is to buy a stock cassette that has most of the gears you want, then an additional sprocket or two to substitute for the un-wanted sizes. Although the Hyperglide ramps don't necessarily line up with non-standard sprockets, as a practical matter they tend to work just fine, even if they make a little click when you shift.
Note, in most cases, the smallest sprocket must have a built-in spacer, so, for instance, if you are converting 12-27 into a 13-32, you'll need to buy a new 13, even though the 12-27 comes with a 13.
The differences in thickness between 7-, 8- & 9-speed sprockets that don't have built-in spacers are so small that substituting 2 or 3 in a cassette won't have any affect on the indexing. Similarly, 8-speed top-position cogs work OK with 9-speed cassettes, even though the spacing is different, because the indexing for the smallest sprocket is regulated by the high-gear limit stop of the derailer, not by indexing of the shifter as with the other gears.
In general, flat sprockets are $9.95 each. 
Most sprockets that have a built-in spacer (generally the smallest sizes, for top-gear use) are $19.95.
We even have a limited supply of threaded Uniglide sprockets for the top gear position on older Freehubs.
For single speed applications, we also carry the Shimano BMX Freehub sprockets, which fit all Shimano Freehubs. See our Singlespeed Page. Call or email for info.
