Car restoration

i have a 1968 mercury cougar and I am trying to get it back up and going. recently I had some engine work and couple other things done to it and when I drive it for a little and I turn the car off it has a runoff and i was wondering what I can do to make that go away. Another thing is that my headlights don’t work and only one turn signal work on each side and the brake lights go in and out and I was wondering if i should find the short or problem with it or just switch it too electronic.

Here’s a good place to start for the turn signals. Everything you wanted to know about the 67 Cougar Sequential Taillights (classiccougarcommunity.com)