If /when using a timing curve for this cam you cannot get the desired centrif curve by just swaping the advanced springs. You will need a minimum of 26deg base timing at idle. That requires restricting the travel of the advance mechanism to 10deg.
(stock is usually 20-24deg)
Look at the posted link on moding a HEI. Look at the picture. It real simple.
One screw restricts the mech travel..(the amount is relative to the sized of the screw head diameter). The other method simply locks the mechansim.
26deg base at idle +++10 deg advance curve 36deg at max advance.
The lightest tension springs give inconsistant results.
But, You will find the locked out timing on this engine, with this cam, works the best.
Save yourself the time and experimentation.