Because single exhaust head pipes for Pontiac V-8's do not exist. I have had a 1968 Firebird project seemingly forever. The Firebird needs to move around under it's own power but I had straight pipes exiting at the doors. Loud enough to wake the dead. I had a 455 "B" body head pipe but it had the three bolt flanges. I need the two bolt flanges because it is 1968 manifolds. So I scrounged around my garage and found enough to whip up a head pipe and muffler. So six separate pieces I used to make this. Gotta love gas welding, it doesn't care if the steel is all rusty. For now baling wire can hold the muffler up. Cost: some welding gas and a few beers.