I was going to say I would like 1-7/8 headers on your combo. I can tell you I run 1-3/4 headers on the 906 headed .557 cammed 440 in my 63. It has run 11.50's as a street car driver at 3700 lbs. I think my combo is fine with the 1-3/4 and may not pick up with larger tubes. I am sure some others will chime in who have tried both sizes. Ron