The stock DP is a double-wall with an internal flex. I have heard of these separating and causing a tick or rattle.
This is another option for a cat that may work with your stock DP flange, and may even fit your car better than the Hogan (because the cat is cylindrical, rather than oval):
Here'* the manufacturer'* link:
(Nowhere does it list what the inlet/outlet diameters are...you should call car-sound to find out)
I'll tell you what, though...you may not need to change out your cat. The stock cat on my '04 LeSabre is a small, ~10" long "bullet" style cat (compared with the 2 foot long, 10" wide stock monstrosity on my '98 LeSabre
If your '01 Bonne has this smaller type cat already, I'd say leave it in. Especially if you're sticking to a stock DP, which necks down to like 2.25" inside anyway