I am in the process of installing a bassani catback and bassani x pipe. I did not recieve any instructions for the catback and I am having problems getting the tailpipes to go over the rearend. What do you have to do to get them to go?
Put jackstands under the frame rail of the car in the back, not underneath the rear suspension. If you support the car this way, the rear-end should drop down enough to allow you to slide the tailpipes in this way.
What Chris said is a very good way to do it, even better it you have a lift because you can angle the entire tailpipe towards the ground and then go up and over the axle. Basically, you want to take the compression out of your springs to lower your axle enough to get the pipes over it. I just helped a friend of mine put a Bassani catback on his 99 GT, and we took the wheels off while the car was up on jack stands, and were able to maneuver the tailpipes over the axles. Good luck, if jacking up the body doesn't work, take the back tires off along with it.