No need to apologise, I'm a gauge freak as well. Had a full set on my Morris Mini, oil pressure, water temp and amp. The water temp saved my engine when a core plug sprung a leak, the standard Mini didn't even have an idiot light for water temp (or a heater as standard for that matter!!) so I wouldn't have had any idea till too late.
Most my VW's had oil temp and pressure as well as head temp, volt and tach, soon showed me the relationship between full throttle flat out running and oil/head temps on an air (and ultimately oil ) cooled engine!!
As a suggestion, you will find 5 bar too low for the Airhead. I'd already shelled out for the gauge and sender before someone suggested the same to me. The Mighty Ninety goes past 5 bar when cold and stays pretty close to it once fully warmed, only dropping when at idle (2 bar) or puttering along at low revs (around 4 bar), this at an oil temp around 110 - 120 deg C. I don't consider it a problem though as it seems more obvious if something was to go wrong.
I must admit though, vac gauges have always seemed a bit naff to me, but each to their own!!!!
Bill.....................;-)