Figured I would do a basic writeup on this since there isn't a ton of complete information on using a fixed back bucket seat with the factory 3 point harness in these cars. I kept the factory pyrotechnic seat belt so I don't have airbag lights.
I started with the driver's side to make sure everything fit, I'll probably do passenger side in the next month or so. Ultimately I want to go 4 or 6 point harnesses so I can use a HANS, but I'm probably going to go after a rollbar before I get harnesses, although I might talk to the HDPE group I run with and see about trying to mount shoulder straps to the rear bulkhead. IDK, seats first because the factory seats are terrible for track days. I can't believe it took me 3 years to do this.
Get the factory seat out. Move it into a high up position so you can get clearance for the bolt where the lap belt attaches to the seat. Remove the bolt/nut at each of the 4 corners, then go disconnect your battery and wait a few minutes. Disconnect the seat harness from the car, and pull the seat out. There's a single screw that holds the silver plastic piece on the belt keeper that you remove to get that out. I pulled the seat out of the car, then took off the lap belt attachment.
Underside of the seat. Unclip the seat yellow seat harness box from the seat. Its a neat little assembly. You can pull the back of it off and remove the connectors for all the ancillary seat stuff (motors, seat heaters, controls). Leave the connections to the seat belt connector plugged in.
One bolt pulls torx bolt holds the seat belt connector to the seat. Take this off.
I used the VAC seat mounting kit. Really happy with it and it gives a ton of adjustability. Mount the adapter to the floor using the factory bolts/nuts.
Ultimately you'll want to mount the lap belt stuff after you get the seat in, but I mocked it all up first to see how it would fit without the seat in there. I also bought the VAC Lap Belt kit, which comes with a L/R lap mounting point. Mounted to the VAC bracket with an M8 x 20mm bolt and washer. I stuck some velcro to the floor and the seat wiring harness to keep it from moving around. I need to go back and put some better adhesive on the carpet side, as it didn't stick very well. Here you can how the lap belts mount up.
Then all you have left to do is mount the side brackets to the seats and then the brackets to the VAC floor adapter. Again M8 x 20mm bolts with washers. I ended up having to invert the outboard side bracket to shift the seat far enough over to clear the door cards and center it on the steering wheel. After I got the seat installed, then mounted the lap belts. I ended up using a nut as a spacer underneath the seat belt latch mounting point to space it up a few millimeters so it would work better with the seat.
It takes some finagling to get the seat belt connector forced through the hole in the seat, but I go it there and now it stays there. Its not 100% ideal because of how low the seat belt connector ends up being, but I'm happy enough with it. The belt connector ends up jabbing into your leg a bit and the seat belt can't flow freely through the connector, but for track use this will probably end up being nice, as you can cinch the belt down hard and it doesn't move.
Reconnect the battery and fire the car up. No airbag warning lights are on since I kept the factory pyrotechnics.
Overall I'm pretty happy with it and I'm going to go ahead and order the stuff to do the passenger side. I sometimes have instructors in the car at HDPE's so I still need matching safety gear for passenger.
Like I said, ultimately I want to try to replace the factory rollover protection with a full size rollbar with a harness bar. There's actually alot more space back there now that I'm using a thinner bucket and I'm on the shorter side anyways. Once I get that sorted, then I'm switching to harnesses instead of 3 point belts.
