[ERA Chas]

AGP,
This does not sound like good raw material to build a satisfying Cobra. And it will be VERY EXPENSIVE to correct its problems to make it so. Examples:
The cut LTD chassis weighs far more than chassis found in conventional replicas. The 460 from a van weighs about 750+ pounds with iron heads and intake. Don't worry about what carb is needed, the drawbacks are far more basic than that.
I don't wish to bear such negative news, but am trying to save your capital and effort on what will be an un-satisfying project.
The best advice is to buy the best quality car you can afford. By spending the money up-front, you can avoid a long, expensive ordeal. Also, you need to study the forums and websites to learn much more about the subject to make informed decisions.
There are MANY good quality, used replicas available world-wide to choose from in the $20,000 to $30,000 USD range, compared to what you're considering now.