My first question is, do you have a diffuser across the opening of the hood scoop? The problem is that air enters the oepning of the scoop and shoots across the top of the first 2-4 stacks. I think it actually creates a venturi vacuum, and sucks air out of the closest stack.
Then it shoots into the back of the engine bay and forces feeds the back 2-4 cylinders. You get a big mis-match in cylinder feeding. This one that I built out of some scrap alum is worth 8mph on the front stretch. That's a lot.
As for cold air, I've been considering that. I don't like the idea of a turkey pan. That requires you to feed the entire engine through the hood scoop. That's not a very big opening.
I'm considering making a turkey pan that's open in the front. Then extending the bottom of the pan out over the top of the radiater. That should provide good air flow without starving it.
To make distributer access easier, I'd make it into two parts and either cut a hole for the distributer, or fab a bubble cover.
One of my many winter projects.