Legion,
Not sure of your year of fitment.
For what it's worth: I have test fitted these:
They fit correctly on 1980 and up FJ45 longbeds.
They do NOT fit exactly on 1967 FJ45 longbeds:
The parts are "sided" and have a pinch pleat that coincides with a matching protrusion in the later upper cabs above the curved glass.
The radius curvature is also different between the 1960s and the 1980s.
Additionally there are no captive nuts that align in this area on any of the vehicles I own, so I will address this when installing.
Apparently the Canadian spec trucks used these plates for seat belt shoulder harnesses, perhaps in the later 1970s. Maybe in Australia,too, but I haven't checked.
Although the USA has/had regulations for shoulder harnesses in existence in the seventies, the FJ45 pickups weren't officially imported here then, so there aren't any USA examples to go by.
Certainly they were not a worldwide requirement.
Lapbelts-only were used in some locales up to 1984 vintage.
Perhaps, like you, I can see the value in a better restraint than simple lap belts. I have seen these before on the Canadian trucks and liked them.
My original plan was to fabricate a similar bracket out of heavy plate, and like these, mount to the top header-rail at at least two or three points around the curvature behind the driver's head, to spread the potential load.
But, as I have more than one truck to complete, looks like I will still need to stick with the original plan for the next truck anyway, unless you can come up with a source for more than one set of brackets.
Let me know if you're successful.
As is ovbious, I can get pretty persnicketty with certain details; that's spelled A-N-A-L. Most folks could care less.
But it's my truck, and my call.
Since you've shown an interest, I thought I'd chime in.
Anyway, hope this helps you.