Header Tube size.

they make a 2" header for a body with a 440. i have heard the you can make them fit on a low deck but they take a lil persuasion.

i dont think you would be giving up 70-80 hp with a smaller header unless you were well above 600hp. if its a 500hp engine i bet you would be loosing maybe 30-40 hp with the smaller tube header. my 383 is stock displacement so i am still prob in the realm of efficient exhaust with the 1 3/4" primary and 3" dual exhaust.