Rear Seat Belt Question

[banpei]

From experience I know that other models/brands might not be suitable for placement on the AE86. The 3 point seatbelts are intertia belts, so they lock up if they aren't within 3 degrees of their designed angle.
For both the hatchback and 2 door the belts are mounted with something like a 50 degree angle. See also in this video:

So as long as you can find belts with roughly the same angle it should work. But keep in mind those belts are there for safety, so make sure you verify if they work correctly. I always say better safe than sorry.