Of course after you have done the work to enlarge the outlets you now need some larger headpipes (or downpipes) to take advantage of that modification.
These headpipes were fabricated using a stub of 2-1/4" exhaust tubing that was flared on both ends. The 2-bolt flange is an original factory piece that's been opened up a little using a half-round file. It's always a good idea to make sure you put the 2-bolt flange on the pipe stub before making the second flare on the pipe.
The bottom flare on the stub makes for a pretty decent transition from 2-1/4" to 2-1/2" tubing. The 2-1/2" 90-degree pieces were cut from some bare mild steel 180-degree mandrel bends that I bought from a parts house many years ago, today I'd make sure to use aluminized tubing instead.
As you can clearly see the old factory 2" crush-bent pipes can't even come close to flowing as well as the new bigger headpipes, the 2" pipe shown here is a rusty original from the right side on a '69 Grand Prix.
