Your first stop should be at your local track. See what their class structure is and what they recommend for you. Some tracks are running 4 cycle engines , some still race the kt100’s , some emphasize TaG setups. They can steer you in the right direction and may have or know of some karts with the proper setup for you for sale. I made a big mistake at the start of our rookie season and bought the wrong kart for my son. He was 12 and going to run in Yamaha rookie and I bought a 32mm frame 50mm axle Biesse kart with a Sr. Yamaha package because I got a “good deal” on it. The kart was way to stiff for him, I had to change the engine over to Jr. with a new clutch, carb and exhaust. The seat was too big and the rear tires were the wrong size. My good deal cost me a bunch of money. I ended up buying another kart, a Margay, with the proper setup for him and I ran the Biesse in Sr. Pipe class and it all worked out ok.
