[G.R.]

I used s/s finish washers and screws--the trick is to not use a powerdriver to run the screws in but to do it the old-fashioned way with a screwdriver so you can control the pressure--just run the screws in until they start to snug down and the washer doesn't spin--all the screws do is hold the dash in place, there is little stress on it so they don't have to be snugged down super tight. If you use a power driver you do run the risk of cutting the fabric or leather with the washer, unless you can control the driver speed and torque.
I've not seen any nice finish type washers with any flat back though there are rubber and plastic types available but they look more utilitarion(sp).