Edit: Buy a seat that is designed to accept a stock 3-point belt. At worst, use the lap portion of a real (not tuner) 5/6 point harness through the seat holes. Also, talk with a real race shop that acts as a tech center/car certifier as part of their business. Doing otherwise puts you at higher risk to serious, if not fatal, injury. Don't end up like that kid who installed 4-point tuner belts in his car and paid dearly for it when he would have been much better off with his stock belts.