Extra gauges I fitted were Turbo boost, temperature gauge for the gear box, as when towing, I thought the box was getting too hot, in the summer on long drives with over two tonne on the back, but I found most of the heat came via the engine, and wasn't that hot after all.
I put these in the cubby hole below the radio, but now my Amstrad 901 (CB) sits there.
I also have an inclinometer, that I fitted a thin bracket to, that clips behind the central vent.
It is difficult to fit gauges and make them look neat, also to avoid drilling holes etc.
A low profile pod that could handle 3 or four 50mm diameter meters would be good, that could sit in the centree of the windscreen on the dash.
Preferably in grey.