Can I use a Fujinon W 300mm (5.6) lens for a 4by5 camera? I'm planning to buy one on ebay. (This lens is made for a 8x10 camera. It's available on a 97x99 board.)
Sure you can. Realize that it will give you the equivalent of a 100mm lens on a 35mm camera but you will also have lots of room for movements. I plan on using a 8x10 lens on a 5x7. Just make sure the lens board will fit on your camera or make one to fit.
That's what I use on my Tachihara 45GF; a Fujinon-W 300/5.6 in a Copal #3 shutter. The combination works just fine and I can focus down to 2.5 metres at the limit of the bellows.
Just got my lens today, and I'm happy to report that the lens is stable with the 4by5 Shenhao. I'll be shooting a couple of pics tomorrow, I hope the shutter doesn't shake the foundations. I will post a pic soon. Lens is awesome!