Yeah I have no idea why its like that, mine is the same pipe but with cats and I don't remember seeing that middle weld. I mean its probably fine. Yes that fits stock headers, just be prepared for the goober that is the bottom passenger bolt.
2000 Mustang GT Steeda #0048 34k miles. 99 Cobra 4V swapped, FTBR IRS swapped, exhaust, tuned by James Gordon.
Just because I give you advice, doesn't mean I know more than you. Its just means I've done more stupid ****.