I agree that the Trans Am guys had a lot figured out, and the current serious Vintage guys have modernized that path, copying what they are doing will certainly put you on the right path.
If you have a sufficient cooling system during track use, you could start experimenting with limiting the air incoming through the radiator, in conjunction with the chin spoiler (to clean up air below the car) to help minimize the air coming in under the hood and reduce the "sail" effect. The backup hood, along with the rear spoiler/spare truck lid sounds like a good option. In the future once I get lots of other things sorted out, I will be sourcing a functional hood scoop and a spare trunk lid that will have a spoiler/foil on it for autox and track use.
Another thing to check out are all of the high dollar classic pony cars that are playing in the Ultimate Street car series .... tons of aero and venting getting added in to vintage bodies to try and keep up with the aero, cd, and tech assist advantages that the modern cars have (C5/C6 vettes, 5th gen Camaro, Mustangs, and GTr's)
Thanks for all of the replies on here, good info
Agreed - MUCH thanks for all the info!!
And that '70 is PERFECT. Seriously. I need a tissue.
I don't have any cooling issues, even in hot/humid traffic. I USED to, but since I added the flex fan, shroud, Water Wetter, and lower valance cut-out ala R model valance, no probs whatsoever. BUT I had an inkling that the hood was acting like a sail...you'd think my first clue would've been that one time before hood pins and it DID sail up O_o. This was at 38mph. It did a number on my original hood, hinges, and inner aprons.
Funny you would mention OUSCI, as I was all set to do the weekend in Portland in July...until they released the schedule for 2015. Nothing in Portland, just Thunderhill at the end of February. Siskyous in February? No thank you. Killed my whole year, as that's EXACTLY the kind of stuff I love to do with my car. And what it's being set up for
. I saw all the final competitors at SEMA, and while a lot of them *were* very high dollar builds, a lot were not. But it was interesting to see their setups at the very least.