I built a sweet go-kart type vehicle in college. I was the team captian for the during the 2003 season. It had 20 inches of independent travel front and back. We could only put a 10 stock briggs and strattion engine in it, as per the sae mini-baja rules. It could hit about 35 mph, even with the little motor. The car was completly built from scrach. We designed the spindles and suspension geometry. I even went as far as to design and build the shocks.
Here is the teams wesite
www.baja.mtu.edu has a couple videos and a buch of pictures. Good luck with your project and any questions just give me a hollar
Jeremy