I love the comment about “headless horseman”!!! Dead of night, a little mist maybe... I can see the open mouths now!!
I usually punch it up a little by adding "long flowing grey hair, rapidly turning to white". Kinda' suggesting a Richard Branford image. In bad light, that's a little disturbing?
Don't forget this is a white "special Mustang" so the image of a mechanical white steed should occur to some too?
On the headers, the originals are a little small but the biggest issue is they have no collectors to speak of. I don't know of any "cheater" 'goose headers but I'd expect there to be some hidden under covers somewhere...not very far away.
It sounds like you don't know, but Curt Voght, owner of Cobra Automotive in Connecticut, did a project of recasting the GT40 iron heads. The 4 bolt GT40 block had already been done.
I'd suggest that you send them an email about these parts. I would have to think those are legal for historic racing since that's what was run in the Cobra and GT40 "team cars" (factory works in Brit English).
Just do a Google search and you will find their web page and contact info. probably: sales @cobraautomotive.com. You will be talking to Scottie.
They race their own built engines. 292 ci., 620hp @8,200 rpm. This on a single Holley and a Bluethunder Cobra intake.
I say he is turning 8,600-8,700 rpm down the straights. Curt says no. 8,200. He even did a You Tube showing the tach.
Curt's dad was a "restorer" of antique items. He made his own parts that were missing. I think of him more as a counterfeiter. Curt followed in his footsteps.
In the You tube, he probably rigged the tac to read 8,200 when it in fact was at 8,700. He gets creative. The harmonics of the engine would suggest a bit more then 8,200.
You want to talk to these guys about an engine or parts to make yours competitive. You won't be sorry.
I do know that they have a "header guy". They might be able to help you with your exhaust issue amongst other things right in house. If you ever are around looking to visit, their workshop looks like the race shop at Holman-Moody or Shelby America did. You name it, there is one of those cars there being worked on. I have to tape my mouth shut otherwise I will just drool constantly.
Webers are certainly a great choice to go with but you need the rest. How fast you want to go, depends on how much you want to/can spend. The entire bunch of them are too fast for me. I just watch from the sidelines, plus I'd have to stop too many times to pee, from the trauma of scaring myself to near death by going impossibly fast of course? Although I understand that there is an entire new line of adult diapers that you can't notice?