ok well i've had a nice productive sunday!!
went to see me mates at rarespares and got two of these:
these are to suit cars that already have belts so they come with all the bolts but no nuts or retaining plates, so i got myself a heap of 7/16 unf nuts and used a piece of flat bar i had in the shed to make a heap of these...
now one thing i will note here is you can buy a kit of these from rarespares but i didn't bother.....
so my engineering requires that i put one of these plates behind all areas where the bolts go through the floors etc and it specifies a minimum of 45x65mm plate of 3mm thickness. I used 50x80mm plates and the flat bar was 5mm thick, i prefer to over engineer rather than use the bare minimum.
so the above mentioned kits from rarespares comes with a barrel bolt which you drill a hole through the pillar from the inside to the outside and then the barrel bolt goes through the outside and the normal seatbelt bolt screws into it. this works fine but then you get a nice 3/4 inch bolt sticking out of the pillar and it just looks crap. so the other option which my engineer advised will work fine is to cut a hole in the pillar below where you want the hole for the seatbelt, then insert the reinforcing plate up into it, then spot weld it in place, then weld the original cut out section back in.
so i took some photos of this as i thought people looking at putting seat belts in might be interested...

so as you can see above, hole cut out below reinforcing plate, then spot weld holes drilled and centre hole also.
so then insert the plate and use the bolt through it to hold it in place while the welding is being done ... please note the bolts in my kit where too long and i needed to space them out otherwise it would hit the outer pillar and probably leave a dint in it!!
so here you can see, plate is welded in place, welds smoothed off and all thats left to do is weld the cut out plate back on.... i am leaving this out till the engineer inspects it.
as you can see, once the belt is installed and interior is over the top, no one will know it ever happened!!
and while we're on the subject
i love my dogs personality
ok sorry, back to the seat belt install
being a ute i don't have alot of options for the reel so i decided to mount it on the back wall of the cabin, as it was a nice flat surface and its out of the way. on the other side of it is the usual reinforement plate.
the bottom section is through the floor again with another plate underneath. i plan to spot weld all the plates on at some stage so i can easily just unscrew the bolts if ever needed and have the plates stay in place, especially the plates in the lower tray section!
i haven't installed the buckle part yet as i have a few ideas about them i want to run by the engineer before i proceed with it, but pretty simply they will be using a reinforement plate up in the transmission tunnel and have stiff but flexable stalks on them that bring the buckle up to beside the edge of the seat like most cars!
just a quick note, atleast for NSW people, if you are planning to do a seat or seatbelt setup like this, you should first have a read through the state rules about them .... theres a few ADR's you have to comply to, things like the above plate sizes etc. at the end of the day though if your fitting belts to these cars which originally never had them, then your going in the right direction

i know i'd put them in my car even if i didn't need to, makes me feel safer!