Look at the collar on the stock pipe. It is just there for the flange to hold the pipe back into the head. It doesn't actually need to be a full wrap. So for the 500 we cut about 3/4" piece off the end of the straight section of pipe. I forget if we wedged it open or if we cut it in half, I think we cut it in half. We spread the arc of tubing until it fit the OD of the header tube, tacked it in place even with the end of the header tube. It was welded on the end full circumference. it was also welded on the splits, but not on the seating surface for the flange. Or get a small piece of scrap that is a close fit, from a muffler shop's scrap. It's just a fitted ring that works as a shoulder. We filed the welded face flat before fitting. As I said, remember to put the exhaust gasket in while building the pipe. It is kind of cool to be doing a one-off.

Before welding. Not my pipe, an internet picture.

 

thanks again