A word of warning. If your gage is dampened (fluid inside), the accuracy varies significantly with temperature. That is because the reference pressure of the gage is not atmospheric pressure but the trapped pressure inside the gage. As the temperature rises, the trapped reference pressure increases. Thus, the needle reads lower pressure.
Ask me how I know.
This small detail caused me to change electric fuel pumps multiple times. To rectify, take out the gage rubber plug and let the oil out. Leave the plug out.