I've run duals and singles as well as different headers. On my trucks I have always liked single exhaust and will never buy headers that are not cereamic coated. One of the hold ups on getting my choptop on the road is saving for headers. 2-1/8 inch primary, ceramic headers aren't cheap. This is on a well built 427, I wouldn't drop too much $ on a stock built engine but I would get coated headers anyway