I'm thinking of making a set of headers for my Dart. 408 small block, F2, Indy 360-1 heads, about 1250-1300 horse using a set of 1 7/8" Hedmans. I was looking at using a W2 flange, hopefully that'll seal better then my old set, in 2" then stepping to 2 1/8 and then 2 1/4 with a 4" collector. How far should I go between step ups in the primary tubes? is 4" big enough for the collector? I've got to run exhaust to the rear axle so a set of zoomies is out. I'll most likely use my Hedman Hustlers as a rough guide line. A member on Moparts did a set similar to this and they look awesome. Any tips or ideas are appreciated.