What is the fastest car you can buy for under 5 grand, US?
Buy a 91Nissan 240sx for 1K. Then buy The Turbonetics kit for 4K. You then have a vehicle with that could be tuned to 600HP. Of course 600 HP would blow your stock engine, unless you built the bottom end. And you'd need to get a fuel controller. But you could get these items, later on. Since it's a turbo system you could just dial in the boost you want (i.e. turn a waste gate and you get more boost). You could safely get 200-210 RWHP. This in a car that weughs 2300 pounds. You do the math. (-:
Another great feature is that you could turn off the turbo and get great gas mileage. With a large V8's you are stuck with the gas mileage you get.
It's a Nissan so it will run forever, too.