Feel free. They were only a "secret" till I opened the hood. Hey, I "cameup" with the idea when I saw a NASCAR upside down in a photo. The pictues are also on the GMC Truck site. Good Luck
Nothing I do will be as beautiful and exotic looking as those headers and its a much different chassis.
This will be DIY headers. I will do some mock-ups of dual headers and single. I will consider dual headers, single header with single merge / collector and also the triple merge of your design.
The exhaust port has no divider and the port is so weak now that I'm very reluctant to divide it.
At least we have some ideas and dimensions from your dual headers to work with. On the dual header where outer pipes were 1-5/8" , the shared ports were 1-7/8". That means 2.07 sq inches on the single and 2.76 sq inches area respectively. I had suspected that the shared port would not require double the area of pipe.
What diameter collector did you run on those?
Also on the single header, its tough to count pipes on those headers, but it looks as if the the share ports are still using one pipe. What are the diameter of primary pipes and merge collectors? (excluding steps, just average diameter of both the single and dual port primary tubes)
A friend was trying to help calculating from mini cooper headers, but I believe that worked out way too large.
The dual header dimensions seem more in order.
BTW, on the intake we did use a divider, starting well past the entry were the port opens up for two valves. I think we would have had more flow without a divider, but less quality.
Thanks,
Keith