how to tell if the distributor drive gear is installed correctly?

if not using vac adv you can use it installed to alter rotor phasing. pump it up till the phasing is dead on or close then in an appropriate area drill a hole vertical into the 2 flat plates & connect them with a small bolt with a sleeve on it in the middle as to keep the plates flat/parallel/inline. take it apart & clean the shavings. reset your gap.