You can start off by reading the rules, which you can find here (click me!!)
Some general thoughts:
- Seats are now certified only with one specific set of mounts. So if you're using the Corbeau seat, there's a good chance that the Corbeau mount will be required to pass tech.
- All mounting bolts should have large washers or hard metal doubler plates. A 4" washer is not too large.
- All mounting bolts should use locking nuts, or have double nuts to prevent them from backing out.
- Harness bars are almost always only for guiding the belts. Bolt the shoulder harnesses to the floor or to the rear hatch area, rather than attaching them to the bar.
- Lap belts should be mounted to the floor, because there aren't really factory lap belt bolt holes in our cars.
- Sub strap(s) should also be mounted to the floor--but not to the same point as the lap belts.
- All belts have a range of acceptable positions, e.g., the shoulder harness is supposed to come back from your shoulder at roughly 90 degrees to your spine. Find these positions out, and make sure your belts are within those ranges. Remember, an out of position lap belt is one of the things that killed Earnhardt.
- Sub strap and shoulder belts should be going through existing reinforced holes through the structure of the seat. Wrapping them around the front or sides of the seat is a bad idea. Lap belts may or may not have their own holes as well, depending on the seat.
Finally, contact the Safety steward of your local SCCA region and have a talk with them about what is required to pass tech. They are usually pretty approachable, and they do know this stuff pretty well...