I will get things started, from what I have seen, there are only 2 headers most people use on 1st gen birds, hedman and hooker. Hooker has the comp (1 5/8") tubes and super comp (1 3/4") tubes. I have the comp, these are 16 gauge well made, but they have some ground clearance challanges, I always take curbs at an angle. I believe that the hedman are 1 3/4" and 18 gauge.