more details on the eng, what cam, what idle speed. ~10-15 BTDC would be a good range and the vacuum gauge method has been used/recommended then with the initial amt known you would want to shorten the dist slots to get 35 total (w vac adv disconnected/hose plugged) then play w the springs for the adv to come in as fast as possible wo pinging at WOT then if vac adv is used plug it in & give it as much vac advance as it will take (3/32" allen wrench) wo pinging at part throttle.