Hi Derek,
I came up with a very neat solution for my seat belts. I got the inertia reel and floor stalks out of a Austin Metro. I found that the reel would sit inside the opening of the rocker perfectly, I then made custom brackets to attach it to the 4 bolt holes around the opening.
Next, I cut the end off the belt and sewed on a steel bolt-on loop. I did this with nylon bonded thread as per original. I then bolted the loop to the bulk head behind the head rest.
This way I have a very simple and neat looking belt arrangement. The belt comes out of the reel, and ends at the bulk head loop. I then pull the male part of the buckle over and clip it into floor stalk. The only problem with this arrangement is that when I want to lean forward, there is a certain amount of resistance because the belt has to slide over my lap and through the male buckle in order to give me the slack. This does not bother me really, although my passengers find it a bit odd.
A way around this would be to mount the inertia reel behind the seat at the bottom. There are steel brackets behind the Fiberglas bulkhead that you could bolt it to, but then you have to have a slot in the bulk head for the belt to come through. I think this is how some of the American cars were.
I recently mounted a twin inertia reel full harness system in this location on my friend Geoff Peters car. It worked out really well. But did require welding various brackets for the loops to bolt to.
One thing is for sure, you do not have to get any seat belt parts from the USA. If you go into your local motor factor or Halfords, they have kits for installing rear seat belts into cars that did not originally have them fitted. These kits are very convenient because you can mount then in any orientation. The little ball in cup device that stops the belt coming out is full adjustable. Meaning you mount however you like, and then adjust the ball in cup bit until it works properly. The metro belts do not have this feature, so I had to make sure they were mounted the same as they were in donor car. If you do get a kit from a motor factor, you will still need the floor stalks from the metro as they are a perfect bolt in fit for the Pantera, and not to long.
Give me a call anytime on 0781 718 7333 if you need any more advise. I will also tell you a MUCH more economical way of shipping things in from the USA.
Johnny