on road or off-road?
If on road, I'd be looking at something like a FSAE car. Most of them use 600cc bike engines.
That would be the best way to properly deal with the 100+hp of a GSXR600. Yes, you can extend a normal kart chassis and put the engine on it, but from what I've seen that just results in a lot of wheelspin. They're not really designed for that much power.
this will be for an offroad kart with ind. front suspen. and swing arm rear. quad tires and 53" wheel base. i guess i can say it will be a big kart. but i dont plan on a whole lot of speed. i want torque and power. acceleration to. not much speed just wanna go about 75MPH at max.
If you want torque then you've got the wrong engine, a large single or V twin would be better. However, if you gear it right it should still be fun.
I'd STRONGLY advise about going to rear independent suspension. The engine is too heavy to mount on the swingarm, and too wide to mount off to the side inline with the suspension pivot point.