Not that I know of for OS X specifically. You might be better off looking at a Linux SCSI driver and then trying to port it to OS X yourself to get a feeling for using IO Kit and the actual implementation of the driver itself.
Why not go look at Apple's source code in the Darwin project for this? Of course you have not said what you want this for, so if you are looking for this for commercial purposes you better make sure that you are not going to cross any nasty legal problems by looking at the code. So if you are doing this for commercial purposes (or looking to combine this with other open-source code) make sure that you can live inside the relavent Apple license.
Doing some reading I found that there is a matching process that causes the disk driver to match up with the proper clients. But I can't find anything that is clear on how I specify the matching parameters. As far as I can tell it would be in a .plist file but now I can't find anything that specifies which parameters to set and to what values they should have. The HelloIOKit sample does this but it is not a SCSI sample so it is not of much help.
Does anyone understand this and if so can you give me some information?
This is not a good place to find help on this sort of thing. Apple hosts mailing lists on http://lists.apple.com, and there are a few that might be good for you there. Take a look at the archives of relevant ones, and post to the one that seems best. I know that there are a number of Apple engineers who hang out there (and probably few to none here).