Yes. And you CAN bolt them in (with some drilling) but don't. You can get a muffler shop to weld them in for very cheap. Weld ins will work MUCH better.
The only things to consider is that they will pretty much preclude a lowered car with a side exhaulst. And check out Maximum Motorsports' and Griggs' subframes first. Depending on your goals the Steedas are fine, just pointing out the alternatives. Subframes are wonderful for the price.
http://www.maximummotorsports.com/ http://www.griggsracing.com/