Stick with the Original German Mauser 98 (or magnum length actions). Magnum actions are made by Precht for Mauser and barreled actions are used by UK Rigby.

I know Granite mountain arms actions have tight tolerances which defeats one of the main attributes of the '98 design: Slop to reduce binding by contaminates. I also understand the US market doesn't understand this and requires tight tolerances.

There was a new complete .416 Rigby Mauser magnum for sale in Brisbane about ten years ago for A$14K.

Try Myalls again. A gun show with lots of 'dreamers' is not the place to get serious. You may have to go in with a deposit. A barreled action maybe easier than an action to import.