with the tooth lined up you want the rotor "plumb" vertical in line with the dist cap "bulge" & closer to the "trailing edge" so to speak of the cap terminal inside the bulge is even better cuz the vac can will shift Rotor Phasing CCW on a SB. the cap terminal width is ~.214" and the rotor terminal width is ~.244" so you have some leeway there as the bottom line is that that distance cannot be greater than what the spark can jump & if so it will misfire plus there is the radial gap between the rotor tip and the cap terminal & if the total of these combined distances bumps the required voltage to jump that gap more than the available voltage your system has then it will misfire, sporadically tho as the can is constantly changing the circumferential "circular" part of the gap. For the radial gap NAPA has a rotor with a .060" longer blade (MO3000) for $8.xx out the door & you can drill out the rivet on yours & make your own longer blade. ideal radial clearance is .015". keep the rotor/cap terminals clean with a dremel as sharp surfaces need less voltage to jump across em.