It's gonna be an offroad cart, were we live there's no flat place to get up any speed. Me and my buddy's built some rails using subaru's a couple years ago and I'm thinking of using that idea but small and light. Here's a pic of the rail so you can get an idea. I have 3 cub cudets with clutch's and driveshafts just no idea on how to get it to a rear axle.
There built out of 80's subaru wagons, we used the complete drivetrain and brakes. We used 27in 4 wheeler tires on wheels we made. The rest is .095 tubing and the frame was made from 2x2 box. Thanks for the link anderKart, I'm still researching a rear axle.