Mapping Arneson's Locations to Greyhawk

[aldarron]

My assumption is that Mosshold is the GH equivalent of Maus, so if the Arneson map is shifted about 45 degrees, we might get somewhere?

I think that, agreed that Mosshold=Maus and a few other obvious locations, there is no big reason why other locations from FFC & Co. should be positioned exactly where they were in the FFC. Pushing them around a bit will work as well and will allow bringing across to Greyhawk a lot of ready made Blackmoor adventures from other worlds of fantasy.
Said that, the other way around can be taken as well: for example, the Clockwork Fortress and the Land of Black Ice could be very interesting tropes to import to a Blackmoor campaign set in the FFC world or on Blackmoor/Mystara.

Yep, as far as I can tell though, there is only one Greyhawk map location of a town that is out of place, so to speak, that being Glendour/Glendower.

You could say Tonnsborg is out of place, but only if you consider it to be identical to Tonisborg, and only if you consider further consider Tonisborg to be at Vestfold. There is no Canon location for Tonisborg.

The City of the Gods is also a bit of an issue, but that's kinda up to the DM since they are described differently. The Greyhawk CoG is supposed to be an actual ancient city under the ice - Blackmoor CoG is a crashed spaceship - there's no reason you couldn't have both these things in separate places. Maybe the locals know the CoG stories and when the spaceship crashes they give it the moniker of the place known from the myth.