I had to slot the tang and the retracters bolted in fine but the covers will not fit now. The fourth gens sit up higher and do not allow them to sit down where they need to. Has anyone else ran into this?

Well I have come to the conclusion that fourth gen seatbelts suck. While they physically bolt in (with mods on the rear), they do not fit well. In the front, even with 1982 sills the receivers don't naturally rest in the opening and must be bent into place. This puts tension on the door sill every time you buckle up. In the rear, you cannot put the covers back on the tensioners. They just sit up too high to allow them to fit.

My advice is to not bother with the belts.

It's nice that the 4th gen front seats fit well in our cars, but I'm not surprised the rear belts don't as I never thought the rear seats did either. Many people here showing how the had to modify the rear seats to make fit, and I've always thought the results look bad.
The 4th gen front seatbelts are supposedly better functioning than the thirds with only an upper retractor, so I would be willing to put more effort into them to get them to look right.
I've been curious about exactly how the floor end fits, haven't seen any pics yet.
Please post a pic of the seat belt mount at the door sill? I had heard people modified the 82 sill to work better. I'm actually starting production on door sills that will be molded with no cut out at all, so they may be a better starting point.

No cut out at all would be perfect, you don't need one. I will get you a good picture for you to see.

Great! That would be very helpful.
When making the mold I was thinking I would make it with the retractor cutout molded in, but I decided a lot of people might want to use them for the 4th gen or race harness seatbelt conversion since the 82s are getting hard to find. I wasn't sure if there would still need to be some sort of cut out for the 4th gen floor mount.
Putting the finishing touches on the mold now, hopefully popping a test pair by next week. Mine will be epoxy fiberglass or carbon fiber, not original texture or pattern. Should be a lot better than the original junk.

Here you go:



See how it is not even close to lining up? If anything a mild cut out further back to fit it, but as it is now I think it would look better with no cut out and a hole in the carpet for the bolt to pass through.

Thanks! Yes I had read the 82 cutout wasn't exactly correct. Looks like uncut would work, but maybe a half circle cut out behind the 82 hole would be best?

I will get a better picture when I have time. An angle looking towards the outside of the car would help a lot. When you buckle up, the buckle is pulling towards the middle of the car so it would not stay in any cut out. As it is with the 82 sills, if you got into an accident you would move forward until the slack allowing them to sit in the sills is taken up. I know an accident would suck either way but I don't want a running start into my seatbelt, lol.

I think you are correct that no cut out would be the way to go then.
Does it seem like the belt would get hung up under the lower edge of the sill? Would a bevel of some kind work? Or does it stand away from the sill enough that it's not an issue?

In your instance, why not dremel the oval hole back farther to accomodate the sest belt guide?

Here is an inside view:



Opening up the slot would not matter because the seat belt receiver wants to naturally sit on the inboard side. You have to force it out to go in the slot and like I said, I don't want a running start into my seat belt in the event of a collision.