I guess it depends on who's answering the tech department phone. I was told that the outlet for the manifolds on the 5.0 and 5.8 are the same size and that the Bassani Y-Pipe for the 5.0 and 5.8 both require the use of inserts to allow the 2.25" Bassani pipe to seal up to the stock exhaust manifolds. I have found several 58150B3 Y-Pipes for sale on the web for $500-$600. I plan on using the Flowmaster Y-Pipe merge collector and adding an oxygen sensor bung to the top of it.
I'm guessing you only have one O2 sensor then? I thought you had two on your '95. I would still put them into each down pipe instead of in the Flowmaster collector. My left pipe is right before the pipe curves toward the center (about 5"-6" from the header) and the right pipe is in just before the pipe merges to the first cat (about 5"-6" from the header too). The third (cat sensor) is a few inches right after my second cat. I just replaced mine with Ford one's this week. Where do you live because if you disable your EGR and go to the hassle of installing the Lightening headers you will never pass the visual for smog, plus you need to re-search doing the "Y" before you waste too much money.
I however think it would be a cool idea to have a second exhaust system that disassembles from the headers back so you could have a custom performance "Y" and a single hi-flow cat 3" all the way to a decent muffler. That way you could keep the stock exhaust for smog every two years and run the better setup in between! If it was all clamped then removing it would be cake and the performance exhaust could still have the O2's so the PCM would be happy and all the shift points etc would remain the same....
The Bassani site says this for the headers....
50 State Street Legal E.O.#D-374.
Not needed is using Bassani Equalenght headers.
Part #150501 Flange rings required for use with stock exhaust manifolds or small collector style headers.
1 1/2" diameter, Equalenght 14g primary tubes, 3/8" thick laser-cut flange with a 2 1/2" > 3" collector.
The site says this for the "Y" pipe......
Legal in California only for racing vehicles which may never be used upon a highway.
It is illegal to remove a properly functioning catalytic converter.
S.S. comes with Metallic Subtrate Catalytic Converters
2 1/4" diameter tube at Y and 3" diameter tube at leg.
That would lead me to believe that their "Y" 2 1/4" would not need anything to reduce the size because the headers are 2 1/2" to 3" but if the "Y" (flanges out) like stock "Y's" then I think they would fit fine, like my stock "Y" fits to my headers....
My stock "Y" fits my Doug Thorley shorties and I have never heard of anyone's Bassani "Y" not fitting their Bassani headers or using rings with a 5.8 only with 5.0's and only with stock exhaust manifolds. There's so much confusion and different reports here it ends up being a trial and error or hit and miss.....