I too use the old style tapered spring. I bend the top of the spring, the part containing the hook, down at about a 30° angle. This makes the overall length shorter. This is important to prevent knuckling when you reduce the length of the tension screw. I also arch it slightly after its in the gun.
I measure the tension on the hammer by hooking a trigger pull gauge in the little notch formed by the bottom of the flat pad where the hammer hits the hiring pin. I pull the hammer back with the gauge parallel with the barrel. At the midway point of its travel, the tension on the hammer measures 2 7/8 pounds. All other tuning is done by polishing the action and playing with rebound springs.
The hammers with the fixed firing pins are measured in the same manner, but you hook under the hammer nose. This is higher up on the hammer so the numbers are different. I've not worked on enough of these to have a firm number.