1. I wouldnt run a harness without some kind of cage in the car. And if its your daily driver i wouldnt put in a harness. They become very annoying after a while.
2. It depends on what "racing" your talking about. Im not really familiar with Autocross. But i know if u plan to race the car in a class they have a billion rules on how to run a harness and a cage and what not. If you plan on only doing HPDE's and stuff like that they arnt much of a stickler about it.
3. id do what AutoX Z said and leave in the stock belt for daily driving if you decide to put a harness in. Not many harness' are
Id say, if the cars a daily driver not to do the harness and just run a nice aftermarket seat with the stock belt, unless u plan on running a cage in the car.
Good luck and be safe
