This setup is also designed purely for Land Rovers with a spare tire attached to the tub's forward bulkhead by the standard original steel spare tire bracket. As well, I believe a knobby tire such as the ones on my vehicle should also be the only type used, as it helps prevent the belt slipping sideways.
I wanted a seat belt for the center seat that had a shoulder strap. For this middle seat, there appears to be only lap belts kits available. A lap belt does not prevent a passenger's head from contacting the metal dashboard in the event of a substantial frontal collision.
Also wanted was something that would not require modifying the Land Rover, beyond the existing seat belt anchor brackets and plates that I've already installed. Keeping this vehicle as unaltered from the original as possible has always been a priority, except where absolutely necessary.
The following is what I've come up with. It's a standard shoulder harness set (from Land Rover), in this case with the retracting spool attached to the very sturdy spare tire bracket, and with the shoulder strap passing upwards and over the spare tire. The tire acts as the support to make sure the belt falls correctly across a person's chest. To prevent the belt from slipping sideways over the top of the tire under a forward load (this slipping might be hard to do under impact in any case, as the large treads act as very effective place-holding channels), the triangular slotted belt holder that is a part of the assembly (the part attached to the hard-top sides on the other belts) is held by a cable which in turn is attached to the steel capping on the side of the tub. The cable and it's fittings are stated as being capable of withstanding 2000 lbs of pull, but as they serve only to help prevent the shoulder strap moving sideways they shouldn't be taking much impact load at all.
The retracting/locking spool, at the center of the spare tire, is tightly anchored in the vertical position, as it has to be in order to work properly.
Below, the seat belts, with the center belt stowed.
Center belt connected. The belt falls across the chest of a passenger right where it should, even for taller children (those too large/old for car-seats and booster seats), and is even adjustable if necessary. The curve over the tire is a little low for the shoulder of a taller-than-average person, and in an impact would force the shoulder down, but in this case I believe it's better than no shoulder belt at all. This arrangement also works with a child's booster seat.
At the top of the spare tire, the connector and cable holding the belt at the angle. Driver's belt is connected to show the comparative angle.
Rear view: Cable attached to tub, and the retracting/locking spool at the center of the spare tire.
At some point, in the interest of having some sort of rear impact protection, it would also be good to find a way to have head-rests installed (without changing the seat style). I'll have to work on that. At a stretch,for the time being a shorter person in the middle seat at least has a somewhat soft tire behind their head in the event of a rear impact.
