the test-pipe just bolts in in place of your cat. you could get one welded up with fittings to bolt to your catalytic converter and when they are finished, unbolt the cat and slide the test-pipe in.

www.testpipes.com

if you do end up getting a test-pipe go ahead and get 2 factory exhaust donuts to prevent leaks and know in advance your car is going to have a significantly different exhaust tone.