I'd stick with Stainless Shanks with Stainless faucets...
You'll never have to worry about leaching lead from the brass shanks as the chrome wears off.
That said... a lot of people have chrome plated brass...me included.
I'd get a shank long enough to go through the material...and stick out just enough to make it easy to attach the hose fittings. If you go really really long...you run the risk of reducing the interior space for your kegs, or getting the rigging (hoses) tangled up.
I don't have a wood spacer...and don't have a problem with Tap handles hitting. I do have my faucets mounted just low enough that the freezer door clears when I use the standard black plastic tap pulls...but I have to open my fridge door before the freezer door with my decorative tap handles.