Doug's or tti's, I'd go with tti's after speaking with several owners of Dougs headers.
While the cost is outrageous, you also get what you pay for and it will be minus the headaches of the normal headers 3 tubes hanging low and becoming dented/scraping the floor.
I disagree with the above statement that a bigger tube header will not make a difference. At this HP level, it will. Though 1-7/8 is a bit far to go. 1-3/4 is plenty.