Thanks to the great information found in threads on this forum, I was able to learn enough to make an attempt at converting from the later North American bumpers (AKA park benches) to the early N.A. (basically same as euro/ROW). But I never saw any pics or specific details so I thought I'd share my experience.
The brackets to which the bumper shocks mount need to be cut off from the body, and some nuts need to be welded into the 6 existing holes in the newly revealed frame underneath. So I carefully cut the welds with a cutoff wheel on my grinder and the weld in the center was drilled out. There are a lot of very thick welds on these brackets. I won't lie, this is a chore - it took about an hour for each side. I was in a bit of a hurry because all of my garage spaces are currently taken so I had to do this work outside... so my grinding is a little ugly but hey, it's all hidden at the end.
Then I bought some M8 weld nuts and carefully fished them into place using a very slender magnet through the larger hole, then screwed a bolt into them to manually hold them positioned for welding. I think the cars with ROW (or early N.A.) bumpers have these weld nuts spot-welded from the factory, but with the lack of access, plug-welding was my only choice. And since my shopmates used up all of the argon, I had to use flux cored wire which explains the sooty appearance. Grinding and painting finished it off, and again it all gets hidden anyway.
I did not fill the holes in the fenders - I don't want to mess with blending the silver paint. You can't see them unless you bend down and look for them. I'll come back to it when I have more time, and make some kind of subtle plugs for the holes.
With the bumper, I acquired the sheet metal piece that sits just below the grille (which I painted satin black and installed), and the plastic lower grills (not yet installed).
I mounted the bumper this morning, and it mounted very easily. I need to wash the car before I take the "after" pics.

It wasn't too bad of a job, by far the hardest part was cutting the old brackets off and grinding the factory welds down. Getting the weld nuts in was actually way easier than I'd thought.