[AtomicLabMonkey]

I don't know what that dinky little upper bracket pictured on the driver's side is, but it's not like any harness mount I've ever seen. Good luck if you try that...

Harnesses should mount to the main cross tube if possible. If the roll bar/cage & seat are designed and installed properly your shoulder straps should be at the correct angle. If for some reason it's not possible with a particular car then you can weld in a separate harness tube behind the seat slots; it shouldn't look like what's pictured there though...