They started out as big block Hooker headers for my 93 C1500 and then came the new header flanges and a meeting with a sawzall. Shortly after I started re-arranging and welding pipes until I got them to fit nice. The passenger side is a real bitch because there isn't much room for the pipes back by the transmission bellhousing! Yeah, 3" collector. I have 3" pipes all the way through the muffler, no reducers at all. The primary pipes are 1-3/4", should have probably got the 1-7/8" pipes but these fit snug enough already.