My Crown Graphic has 323mm of bellows draw. This means you can focus a 162mm lens to 1:1 with this amount of bellows. The G-Clarons, Apo Ronars, Artars, and others of this ilk will be excellent performers at 1:1. However, none of them in +/- 162mm will cover 4x5 at infinity; kind of a large expense for the occasional close-up shooter.
If your Fuji 300 is a Copal #1 shutter, you can get adapters that will let you screw a standard Leica thread 39mm enlarging lens into the shutter. EL-Nikkor enlarging lenses from 135mm and shorter use the standard Leica thread. The longer ones use a flange and won't work in this situation. If your shutter is a #3, you can get SK Grimes to make you an adapter. He charged me approximately $50 plus shipping. You unscrew your lens elements from the shutter, and install the enlarging lens in the front.
A 135mm enlarging lens will get you down to 1:1 very nicely, and for pretty cheap. It will do double duty as a good enlarging lens for the 4x5 format. I use mine in this fashion.
I also need an extended lens board for my Crown Graphic, so I can use my 300 Apo Ronar, and calibrate my range finder. I need a board extension of 75mm or more. I'm sure it can be made by SK Grimes, etc, but the cost will probably be stiff.