GAUGES...Under dash or on top of dash

Personally, put them where it will be easiest to see them when you need to.

I had some mounted under the dash below the ash tray and I found it a bit difficult to keep a eye on the gauge while watching the road. Found myself looking down a lot more than I probably should have been. I agree with Steve, that its easier to hide the wiring, and mount them.

I eventually got rid of them and installed all new gauges in the dash to replace the old cluster.