As said: red to coil neg primary. gap/dwell/point life are inversely proportional. You can set the gap pretty much anywhere you want it (.017 is a good ballpark) just keeping in mind that longer dwell time/smaller gap give more power and shorter point life over time (good for high perf) as you'd be changing em out sooner as needed. For max power set the gap at .005 & if it will start then that will give you the most (as said) coil saturation time for the most power and the shortest point life over time cuz with the points touching/current flowing there is more time for them to burn (over time/wont happen overnight) & if it wont start at .005 go up in .003" deg increments till it will start. For Grandmas' DD you'd want the largest gap for the least dwell time (I'd start at .017 & maybe go up to .020"}. Perf point sets are as you know higher quality & likely have more spring tension for bounce resistance at higher RPM's