I don't think the primary tube size is as restrictive on alot of Pantera headers as alot of the collector size .I had a set of "Big Bore"headers on my car and the collector wasn't even 2".I think the collector and the tailpipes have to be atleast 2 1/2" to be effective.
Rolling Thunder:I think your car would benefit from more compression and camshaft.I run flat tops with closed chamber heads and a camshaft with .550" lift and 235/240deg @.050.I also run a Blue Thunder intake .My car made 340 hp at the wheels with a 750 DP and no tuning.I have Hall 180 headers with 2 1/2"Flowmaster mufflers.I don't think they make any more HP than a good set of aftermarket headers but they sound and look AWESOME!I did see a noticable gain with the Blue Thunder intake over the Edelbrock I switched from.Hope this helps.
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