I might have a part you can use.
I snapped 4/6 of my y-pipe studs when I tried to fit my new car sound OEM replacement y-pipe.
When I removed my manifolds to try to get the studs out, the manifolds were warped.
I gave up and bought some SLP headers and put them on with the Car sound cat.
So I have an extra y-pipe. It is made by carsound / Maganaflow. It is a replacement for a '93-97 single cat camaro. It is the stock dia, but has smooth bends without wrinkles. It is 409 stainless steel, 409 is still printed on the tube. It has the three bolt flanges and flared ends that fit the stock manifolds.
I also have the stock 95 single cat OEM converter with 90k miles and 10 replacment GM y-pipe studs and nuts. You could hollow out the cat, and you should replace the studs they snap like candy canes..
I don't know if the fit will be better or not, but it would be a good starting point for a custom setup.
Most aftermarket y-pipes would be larger tube this is the stock 2 1/4. SLP is 2 1/2. The smooth bends would flow better also.
I would send you the whole works for $75.00 plus shipping. I have the factory box, all I used was the converter since it would clamp to the SLP headers.
Let me know if you are interested.
Z28