lets work w what we have. Want vac adv. look at the chart in the archives for how long to file the slots to & use a rattail file to elongate yours. If you are comfortable w 18 initial then want ~8.5 dist degrees to give 17 more at the crank. reportedly the archive chart is close but not dead on so go a bit less to start w and I'm sure the springs will need to be changed so you will be back in there and you can grind the "tips" of the weights to slow the curve after you get the total set in lieu of sourceing a heavier spring as 2 light MP ones MAY be too fast as is but the subsystems must b done in order. initial/total/springs/vac adv