quick disconect steering wheel???

look on ebay for "NRG STEERING WHEELS"

they make a very nice quick release in 3 different varying thicknesses, they are mainly set up for 6 bolt aftermarket wheels, like momo, sparco, and thier own wheels.

A little pricey, but its a solid mount.

For racing purposes, or as a theft deterrent?

If you're looking for one as an anti-theft trick, don't bother. There's lots of other (better) ways to go about discouraging theft of your vehicle. One of those pedal locks and/or a fuel cutoff switch is usually a good way to go. A steering wheel disconnect has two potential problems from what I can see:

1. Having that come off at a really inopportune time can result in a serious wreck;
2. What's to stop some random chump from just bringing his own steering wheel and plugging it on there, if he wants your car badly enough to actually try stealing it?

As far as other ones, check Jeg's and Summit racing. I've seen circle-track steering wheel quick-disconnect kits in their catalogs in the past, although I dunno if they're model-specific at all or just universals. If nothing else, I'm sure they could order a model-specific kit through Grant for ya'...

Here are a couple mentioned in one of the catalogs I have.

http://www.spatechnique.com/product_pages/steeringquickrelease.asp
http://www.tekniqauto.com/US/snapoff/snapoff.htm