Yup, it looks like that spring is cooked. Is it rusted? or is it overheated to a point of weakness?
The spring should keep the relief valve shut until the pressure exerted on the plunger is about 50 psi or so, per this service bulletin.
https://www.teae.org/cars/bulletin-66-6/
I don’t know the spring k-value off the top of my head. If you don’t have another relief valve to use for parts…. You could arrive at the new spring by a little math and experimentation.
You can calculate the area of the relief valve plunger in square inches.
A = Area (in square inches)
d = diameter (in inches)
A = 3.14 * (d/2)^2
Then convert pressure required to open the valve in pounds per square inch to a force in pounds. Select a spring and try it on your bathroom scale. Assemble the pressure relief valve then press on the plunger. When the valve reaches the open position read the scale. Try different springs to get the expected force you calculate below.
T = target pressure opening (in pounds per square inch)
A = area of the relief valve plunger (in square inches)
F = force on the spring required to open the valve (in pounds force)
F = T * A
Then use the modded adjustment on the outside to tweak it in once installed in the car. This will adjust for leakage and tolerance in the mechanism.
Don’t set it too high, which will result in an explosion of your oil pressure gauge… or too low which will result in poor oil pressure to the engine bearings (which is what you are trying to avoid in the first place).