That's right!
From my purchase of my 1995 3.4 Camaro 50K mile V-6, I also got the original "Y" pipe assembly with the used 50K mile AC Delco CC.
Recently needing to replace the crappy aftermarket CC on the 1985 Firebird, I looked at this option.
I measured it (2 1/2" in & out) and it was also the same length, too.
NOW my Firebird came with a replacement CC item.
That replacement CC was welded on the front pipe & bolted to the back "I" Pipe (which in 1985 is a 2 1/4" "I" pipe), thus all original support brackets still in place.
The used 1995 AC Delco CC has all these exact same bolt holes there, also.
This project was literally a matter of using a muffler saw at front of replacement Crap Convertor, unbolting same item from back "I" pipe, slip fitting the used AC Delco 3.4 CC onto the front "Y" pipe (using wood & hammer for "adjustment!"), obtaining proper length bolts for clamping back to the "I" pipe, reattaching other bolts to exhaust support strap, which all went exactly in place on this 1995 AC Delco CC.
NO TRUE EFFORT AT ALL!
I even reused the wonderful front clamp supplied by GM for holding the 1995 3.4 4th Gen AC Delco convertor in place.
Started the car and SMOOTH IDLE NO RATTLE.
When the aftermarket Crap Convertor dropped, clunk crap fell out. Yes, your aftermarket Crap Convertor can break up from within & propell itself down the exhaust system to clog up your muffler. I saw the truth.
IF ya hear your CC rattling, don't wait forever. You may not get a chance as the inside CC stuff can break up, flow to clog up exhaust, enough to prevent car from running.

I know my car regained lots of pep! Especially at top end and he charge to it!

I'll also suggest you may also use a factory AC Delco CC from a late model FWD car or a 4th Gen 3.8 powered ride, too!
COMMON SENSE SAYS decide if the desired used CC is of good quality.
My 50K mile Used 3.4 4th Gen CC, looking inside, looked brand new (Holding up to sun confirmed my suspicions). The next CA smog test will confirm my use of this option.

A late model factory AC Delco CC is a very Hi Flow item. Especially at 2 1/2" in & out size!

My next exhaust project is to use the 1995 3.4 "Y" pipe set up, as those pipes are larger than the original 1985 2.8 "Y" pipes (which I am still using). I believe going from a 2 1/4" "I" pipe to a 2 1/2" "I" pipe is wasted effort at this point. It's uncorking that crappy original 1985 2.8 "Y" pipe that will make the most HP exhaust flow gain!
ONCE the front "Y" pipe operation is complete, then I'll reconsider going to a 2 1/2" "I" pipe. My 1985 Firebird uses a 2 1/2" Z-28 Muffler (made by Arvin who supplies most OEM muffler stuff to manufactures), so I further helped reduce my back pressure that way.

Yes, my car now emits a most pleasant exhaust note!

 

let me know how you're gonna get the 3.4 pipe to clear the subframe

 

That's easy.
BUT I need an off the car 3rd gen "Y" pipe.
I will not disturb the location of the ox sensor, notr that bend around the 3rd gen subframe.
I will CUT the end of the 4th gen pipes, intergrate it to the 3rd gen stuff.
I only need find the off car 3rd gen "Y" pipe for mock up then on the car 4th gen pipes goes. I want to find a 2 1/4" "U" bend pipe or ? for mock up.
My idea is to create a true bolt on set up using the larger 4th gen "Y" pipes, as ya said they "clear all stuff, including the depth of the undersideframe, UNTIL that bend around the 3rd gen subframe to CC connection.
Again the 4th gen CC is a perfect fit, length, width, height, it does not hit ground at all & is tucked up so pleasant.

 

you gonna cut the 3.4 pipe at the junction & weld up new "bend" to clear the subframe & connect to the cat & I pipe?

Which O2 sensor location are you using? I'm using the pass side exhaust manifold one.

 

you gonna cut the 3.4 pipe at the junction & weld up new "bend" to clear the subframe & connect to the cat & I pipe?

That's the Plan, Stan!


Which O2 sensor location are you using? I'm using the pass side exhaust manifold one.

In California, I will run into less trouble if I keep & use the current location.

Help ya?
I see wheels a-churnin' & ideas a-brewin'

 

word to ya motha

 

I keep hoping to spy one 3rd gen V-6 "Y" lying on ground in local yard.
I don't have time to experiment with pipes on car.
Mock up, fine tune on car SURE!
What's another bend & merge on the ends of this 3.4 "Y" pipe?
That all that seems need be done, true?
Think 4 tube into one collector of Small Block Chevy headers.
These 3.4 modified "Y" pipe can become "Long Tube" extensions, which increase bottom end torque.
True?
I kept this 3rd gen pic for ideas.
I'll take the 3.4 "Y" pipe pic in AM for comparison