Well, you have changed a lot at the same time, which now makes things a bit more difficult to diagnose. The
+ is supposed to be connected to the B/W wire coming from the kill switch, the NEG goes to the switches, be it breakerpoints or transistors. Sure you connected the right plugwires to the right plugs? Intermittent grounding breakerpoints (when they shouldn't) and faulty condensers also can cause problems. In case you have the stock ignition setup, I'd first check breakerpoints and condensers. Open the ignition cover. First check if breakerpointgap is still correct and also that the forked connectors at the back of the breakerpoints are not accidently touching the plate. Then, with engine running, see if there's excessive arcing at the breakerpoints. A tiny bit of sparking is normal, excessive sparking is not good. See
In this vid left condensor (1+4) is bad, right condensor (2+3) is good.
Was the advancer taken apart by any chance?