I get, with 400 hp, 5g cornering at 200 kph, 320 kph top speed, is only achievable even with the aero of a fully enclosed body if the vehicle weighs less than 270 kg, and has tires with mu of 1.5, roughly F1 tires.. peak cornering would be at 260 kph, 7g.
So a fan car might do it with a more reasonable weight, or else you will be looking for tire sponsors.
with more sensible tires mu=1.1, and a /peak/ latacc of 5g at 270 kph, the allowable weight increases to 320 kg, including driver, seat, tires, fuel, helmet and steering wheel.
If you insist on open wheeler then the first car would have an allowable weight of 180kg, and the second, 210 kg.
So the answer depends a fair bit on exactly at what speed you want your 5g-it obviously starts at tire mu at low speed, and then rises to a maximum before the engine power is insufficient to maintain speed at that lattacc.
I'd add that having done the concept calculations for a fan car, you might be surprised by the power required, unless you can fit a decent sized fan.