Aloha Dan,
Like Mickey said. Use the knurled nut adjustment on the end of the vaccum advance to retard the timing by turning it clockwise. There should be letters "A" and "R" on the distributor body just forward of the nut, so turning the nut toward the "R" will retard timing. With the engine warmed up to operating temperature, on the road excelerate from 30 to 50 MPH in top gear, if pinging is heard, retard the timing and repeat the road test. Continue this until the pinging disappears. Usually the best inital timing, using the static method is somewhere between 4 and 8 degress BTC.