as to there probable location. Pressurizing will not reveal leaks at the valve covers since the oil is no longer pressurized once it leaves the valve train onto the cam lobes. All you can do there is regasket the covers.
Pressurizing will reveal leaks at the oil filter, oil pressure sending unit, front and rear crank seals and a few other locations and 5psi is reasonable for searching since oil pressure is 20 to 80 psi.