Possible Electric Problem?

I just got my 89 gt back from getting a freshly rebuilt engine installed. It will run fine sometimes and not so fine others. I can be driving 55-60 at steady throttle and it will die and start right up within maybe a second and the gauges on the left side go haywire, then run fine again. I have noticed that every now and then when i turn the key....nothing. it will do that a few times then start up like a charm. This leads me to believe its the ignition box, does that sound correct to you guys? Im also going to replace the IAC seeing as how thats practically the only thong on the engine that isnt brand new

Lmfao i didnt even catch that when i went over it. It took me a little while. Might be a thong in the backseat but not on the engine

I wonder what it is. The tach never really worked, just shoots up to 4k and stays there until i go past 4k rpm. Also the little washer fluid light flickers. Im guessing something is loose but idk what