Slow Restoration, Starting With Engine - Options?

Appears that you're doing ok. You would expect the pressure to be high until the oil thins out with temperature. As long as there is enough pressure to keep an oil film between the metal surfaces at all speeds and temperatures, everything is fine. Pressure goes down as the engine wears, mostly because the oil leaks out from between the bearing and journal faster. Oil viscosity breaks down as the oil ages too, so be sure to change the oil regularly.

A mechanical gauge uses a Bourdon tube, if you are interested. Pressure measurement - Wikipedia