Gauges read more dependably when the maximum expected reading is in the center of the range.
For example, if you expect boost levels of 10-PSI, a 20-PSI gauge would be best.
Also, it matters not what the gauge says it is for, be it water-pressure, fuel-pressure, oil-pressure, boost, air-pressure, or whatever, they are all the same.
My fuel-pressure gauges all say "water pressure".
I have a 200-PSI oil-pressure gauge that is for on-board air.
I still can't figure the fear of high boost pressure in the IDI engines; I believe it would take a lot more to blow a head-gasket than many are running.