Firewall-to-Fender Brace Rods

[MiraclePieCo]

I've noticed that lots of owners delete these rods from their trucks, especially those with V8s, apparently with no ill effects. How necessary are they? Will fenders sag without them? Is there another way to compensate for their absence - say an additional brace across the core support?

The reason I'm asking is because it appears that my firewall-mounted brake booster may interfere with installing the brace rods. Can I omit them?

Here's a pic of some: