Having done projects like this, I have one thing to say to you:

SNAP OUT OF IT!

First off, that car looks like it will be an aerodynamic pig. The big frontal area, sloping rear, tumblehome and pointy tail look slick, but will result in high drag. If you were serious about building a vintage German aerodynamic design, then the car to build would be the BMW Kamm back. It was a milestone with regard to aerodynamics, but not much to look at:

BMW 328 Kamm Coupe (1940)

http://ae-plus.com/milestones/wunibald-kamm-helped-define-modern-day-aerodynamics/page:2

As far as budget, you'll need a kings ransom to build that car and make it work. I would budget $250,000 with no complications. And there will be complications. A Lesco transmission will probably cost your whole allowance, much cheaper and better to use a BW T5, and hunt up a set of straight cut gears.

After you've spend a quarter mill on the body and chassis, do you really want to use an SBC crate motor? At least use an M3 motor. But let me stop here and say again:

SNAP OUT OF IT!