Hey Hambone

If you go to Juliano’s seat belt site, and look at the install pics
you’ll get a good sense of how to install the upper shoulder belt
Retainer that needs to be bolted or welded ( in my case).

That retainer brace is quite narrow and should be very doable in your
Burb.

In my case I elected to surface weld it since I was upholstering over that area
anyway. But, as you’ll see in the pics, you can fish it up into place behind the interior
Sheet metal if the situation allows....
Hope this helps.