go kart plans are available sa internet (just google it).

i have yet to see a local group/shop do it.

wouldn't it be safer to just buy a chinese ATV - it might be cheaper (P16T to 30T) and lesser hassle.

why cheaper:
1) cost of engine - surplus from a/t motor scooter P5-8T na
2) cost of frame plans - US$ 50-100
3) cost of labor and metal tubing materials to do it - probably another P5T at least
4) cost of other parts like seat, bearings, wheels, brakes, cables and levers - probably another P5T-8T.
5) time mo pa supervising and buying the parts and coordinating things to finish it up.