Is this for an existing neck or one you're about to order anew?

>"Has anyone tried the 1.75" Earvana Gibson OEM nut on a 1.75" USACG neck with with USACG's Earvana nut slot? Does it fit and work well?"

Yes, and yes. However, the Gibson-style nut shelf is only available on tiltback necks, AFAIK. (I would love to be wrong about this, BTW, because I'd like to order another neck, and the tiltbacks still aren't available.)

Problem with the Fender-style slot is that Earvana doesn't sell their OEM nuts in a 1.75" width....

>"On the Earvana site it says of this nut "must cut 3/32"from fret board".... Is this in fact what USACG take care of when with their "Earvana OEM nut slot"?"

Yes.

>"Any suggestions for other 1.75" nuts that would fit well, perhaps from Graphtech? Presumably these would require USACG's normal nut slot, either flat bottom or curved..."

Graphtech also works well, but lemme tell ya: you'll need to sand and file all of these - even the ones that come "pre-formed." They're much too wide and deep, and you'd like to keep your slots as shallow as possible. It's probably worth the $30-50 to have a tech help you if you don't want to invest in slotting files. Better to have good action and intonation than spare the money.

-Ben