early A-BODY 1-5/8" x 1-3/4" SMALL BLOCK STEP HEADERS

Wow ! the reviews aren't looking good . let see some more . I have a stock 65 formula S car so the tubes are going to be tight around the bars . I had #450 dougs on another 65 dart the bars rubbed also and the brake proportioning valve had to moved some . I have hookers semi fender wells on my barracuda now . They fit pretty nice ! they have a few slip on tubes . 1 5/8" tubes -- 2.5" collector.
Would there be any advantage with the stepped tubes and 3" collectors performance wise
?