I just finished installing my new retractable Stahl seatbelts, purchased from Skandix, in my 122 2 door. I thought I would share my experience.
First, the instructions were in German (I think that was the language), but with the illustrations and a little common sense I figured it out.
Since Volvos have a single bolt down location for the base, the instruction illustration shows that the loose end of the belt must be attached with the same bolt that holds down the retractor. The loose end is bolted down underneath the retractor. This results in the part of the belt that you normally grab to pull accross your body being underneath the part of the belt that goes to the retractor. This works, but is a little awkward, since no other seat belt is like that, and it is instinctive to grab the portion of belt that is closest to you.
I found a solution to this. I purchased a spacer from my local hardware store, and attached the loose end of the belt to the outside of the retractor. The spacer I bought was 3 inches long and I had to cut it down to 2 1/2 inches, so that it didn't stick out too far. I also had to buy a longer 3/8 inch bolt (4 inches - I think). The base bolt was inserted in this order: flat steel washer, fist half of two piece nylon washer (supplied with belt), loose end of belt, second half of nylon washer (these two nylon parts allow loose end of belt to swival), another flat washer, 2 1/2 inch spacer, retractor frame, and then screwed into the original body mounting hole.
The result was a belt that works as good as one found in a new car, I am very pleased.
Tom