Here's my not expert advice after going through this 2 years ago. Wally's harness bar is excellent, but I don't know if he still has them available. SafeCraft makes one that works well, so don't let this slow you down. I bought SafeCraft 6 point harnesses. Talked with Ed Sims quite a bit about it. I bought the clip in systems. If you go to the SafeCraft website, you can pick and choose colors and types of belts. It makes it easier if you buy the Brey-Krauss mounting brackets, but you will need slightly longer bolts to mount them to the seat after removing the original seat belt bolts. I also had the Brey-Krauss brackets altered by enlarging the holes a little to fit two clips from the belts (lap belt and sub belt). Order the lap belts as "pull-up" rather than pull-down, easier to tighten and have them done on the outside belt rather then the tunnel belt. I'm 5'11'' and 175 lbs so the standard sizes fit just fine. Order the aluminum hardware. The shoulder belts should be the type that you loop onto the harness bar. Go to the Sparco website to see how to mount them. The release latch is a matter of preference. I got the one with the lever cam and have been happy.
Here's what I ordered and have been happy, but they are pricey since you probably want two sets for driver AND passenger (otherwise no instructor will get in your car).
Red polyester, lever cam buckle closure, sewn, clip-in lap belts-left pull-up driver's lap belt, right pull-up passenger standard length, dual 6 point single tang cam only sub, individual shoulder, 3 inch wide, wrap around with adjuster, standard length.
When you go to the website and look at this, you will understand a little better what this all means. If I'm not mistaken, every belt is dated and is good for 2 years, then the webbing must be replaced to be used on the track. They do check at the tracks.
I also orderd an Arai gp5w helmet and have been very happy with it. Do internet shopping for helmets.