It's separate. The headers come with OEM connect adapter pipes which size down to allow it to connect to a stock catback. You need the 3" pipes if you're going to hook up to the GT500 Borla ATAK system.
Is it the “Kooks 3" x 2-3/4" SS OEM Connection Adapter (2020+ Shelby GT500 5.2L) - 11563000”?
Do you think those adapters would work with other brands of headers?
It's possible since they all connect in the same area but different brands have different lead pipes. Kooks are different from ARH for example.
I contacted Stainless Works and they recommended the aftermarket connect option because it’s designed to fit 3” aftermarket cat-backs. The connecting pipe adapters I currently have on, in order for the gt500 system to fit on the Mach, neck down to fit the factory mid pipe size. I originally thought I could go with the factory connect headers and fit them on with the Borla adapter that’s already there, but I also assume I could remove the adapters and use the aftermarket connect with the 3” system. What was your reason behind suggesting the factory connect option?
The factory connect will bolt right onto the Borla exhausts. I sell them all the time. The aftermarket connection pipes are 3" unless your Borla catback is full 3" without a neckdown they will not fit. Factory connect to the Borla catback will be plug and play with clamps no welding.
the 2020 shelby system uses a facotry connection point style, the same as the gts... they all use that neck down slip clamp style
I actually have mine off of my car currently. Here are the Kook's 3" lead pipes going to the 3" Switchfire.
