[rrobson]

That or buy a drivers seat from a lhd car.

But in any case, an 8.8 grade m10 fastener had a minimum ultimate tensile strength of over 5000kgf. You would be more likely to pull the threaded insert out of the floor as opposed to shearing a fastener. And if you were in an accident with sufficient force to do either of those it would almost certainly be fatal due to deceleration forces.

So crack on, a couple of spacers won’t adversely affect the safety of the standard fitted items. A full runner length of 50mm x 25mm square hollow section would be a neater job over four spacers

And you could use any fastener really, a hexagon headed bolt may not fit but a cap head or Allen headed bolt should be fine if you can’t find any suitable length torx headed bolts