there is no point playing with weights and springs till you know where you are going with your curve

first you need to know what duration your cam is to get your static advance and idle rpm settings 270=10/12@600/700rpm
280=12/14@900/1100rpm
290=14/16@1000/1200rpm
300=16/19@1100/1400rpm

then you need to estimate your total advance wich is relative to your combustion chamber (has to do with burn rate)

open wedge=36 to 38 deg
heart shaped=34 to 35 deg
closed chamber=38 to 40 deg

then you need a distributer recurving machine to spin the dissy till you get it advancing at your requirments