I'm getting ready to put some Euro bumpers on my 73.  Found the unused mounting points on the frame, should be good to go after chasing the threads out.  

Bought a pair of 70-72 brackets, but not sure which bracket is for the left or right.  Looks like the frame holes are offset a bit and may raise or lower bumper a quarter inch or so.

I searched, but came up empty.  Which is which?  Or does it matter?

Thanks

There's no left or right to these brackets. I suggest you leave them a bit loose on the body during the install and make the final tighten after you have the bumper correctly positioned.

https://www.google.com/search?q=240z+bumper+brackets+orientation+classiczcars.com&rlz=1C1BOFA_enUS494US494&oq=240z+bumper+brackets+orientation+classiczcars.com&aqs=chrome..69i57j0i333.22572j0j7&sourceid=chrome&ie=UTF-8