You can use the stock bolts.... but read the countless threads on exhaust leaks and upgrade your header bolts. Once those oem bolts are loosened it is just never the same.
I originally had new ford gaskets with the OEM bolts and sure enough I had a solid exhaust smell within days of the install of new headers. I later upgraded to stage 8 bolts - all fixed! Do it right the first time and get stage 8 locking bolts so that you don’t have leaks. https://lmr.com/item/M9432A54/96-04-Mustang-Stage-8-46l-54l-Header-Bolt-Kit
You can use the stock bolts.... but read the countless threads on exhaust leaks and upgrade your header bolts. Once those oem bolts are loosened it is just never the same.
I originally had new ford gaskets with the OEM bolts and sure enough I had a solid exhaust smell within days of the install of new headers. I later upgraded to stage 8 bolts - all fixed! Do it right the first time and get stage 8 locking bolts so that you don’t have leaks. https://lmr.com/item/M9432A54/96-04-Mustang-Stage-8-46l-54l-Header-Bolt-Kit