It would help if you would describe your interior setup. Do you have a fixed back race seat or stock seats? If race seats, how do you have them mounted?
Typically, shoulder belts are looped around a horizontal harness bar (do not drill holes in this bar!). Laps should be mounted with weld in plates on the structural side sills. Subs take less load (they really only prevent the lap from riding above your pelvic bone in an impact) and can be mounted with backing plates through the thin floor sheet metal. If you have VAC style aluminum seat mounts, Schroth makes a clip that can be mounted to the seat mounts.
https://www.schroth.com/en/segments/.../b-23-kit.html
As for passing tech, read your rule book!