hello....Mike told me they are stepped headers....1 7/8" to 2" to 2 1/8 "....the header i am making is using same step sizes- i am also using stainless steel Merge collectors .....going into a 3 1/4" collector-from a 2.5" "cone"/venturi.......I got the Merge collectors from a set of NASCAR V-6 headers....have fun......
Lee
