I assume you have a racing seat that has the holes needed to use a 5 point harness. you can get all the hardware you need from HMS motorsports. They import the Schroth belts which is what I use in my race car. If your belts have clip ins for the lap belts, they sell some special hardware that you can use to mount the lap belt to the transmission tunnel. it included drilling a hole and using a backing plate.
2014 GT, Track Package, Deep Impact Blue. Roush Axle back, MGW short shifter.