I would suggest: (1) setting initial with vac gauge method (2) shortening slots for the std total (initial+slots) for your eng type (ie 35 for SB) then (3) mix/match spring combo so you are just under the pinging point at WOT up thru the gears on your hottest/driest day no matter what RPM it maxes out at then (4) plug in/adj can. To ans your Q here is a chart