Leave the coil PLUS wiring completely alone except for the NEG which of course was to the points and maybe a tach
The ECU power wire goes to the "high" voltage side of the ballast, IE blue. One side will have brown and blue, that is to the coil. If any question, pull the connection you believe it to be off the ballast, and confirm that wire has "battery" when key is in run.
Make DARN sure both the regulator and ECU are grounded. Scrape away paint behind the bolt holes, use star lock washers, and consider upgrading the engine to body jumper. I like to use a short "starter cable" that is eyelet--to eyelet about a foot long. Bolt it to the holes in the rear of the driver side head, and to the firewall. One way is to the master cyl. stud
