The drilled/tapped mount holes on the receivers should be identical on the 500/590 and the 930.
I've used the same rail on my 590 and 930. Still think you're overthinking the sight set-up though. The reason they call it a "ghost" ring is because it's supposed to disappear when you focus on the front sight. Without it, the vent rib itself directs your eyes to the front sight and acts as an alignment tool. Seems like you're trying to fix something that ain't broke, but that's just my opinion. A wise man once said, "It's your goat. You dress it up however you like"...