The standard 5" 1911 spring is 16lbs. If you are loading close to factory specs, no need to change the weight.
I am not sure what the 3" and 4" weights are, but someone will be along and answer that shortly I am sure.
Endowment Lifetime NRA Member, Certified CCW/Pistol instructor.
"To preserve liberty, it is essential that the whole body of the people always possess arms, and be taught alike, especially when young, how to use them". – Richard Henry Lee 1788