This issue has been addressed a number of times before, so You're not alone. 67Dart273 has posted the wiring diagrams a number of times, get that first, then check
the voltage working Your way from the feed through the bulkhead at the connections in & out of the ign etc. looking for a drop. Back out through the bulkhead and on.
Sometimes I have to use a headlamp with leads and a probe, it should lite bright the whole way from one end of the system to the other, it's a good "load fail" indicator.
It's easy to light a tiny test lamp/led, and to that end You would really go right to the regulator first and check the blue wire key in "run", bright headlamp and good V
(within .4 of V at the Batt) then the problem lies elsewhere. If You've got points, unplug the dizzy so 'Ya don't burn 'em up while testing.....................................
