1998 Pontiac Grand Prix Nothing working in car.

I just replaced my engine with a used one. After I finished I started it up to burn off oil and stuff that dripped on the outside of the block. It started right up on the first try and ran great. I stopped for the night and came back in the morning to finish letting it run, put the hood on and bleed the breaks. It wouldn't start, the gauges and the lights in the dash do not work, nor does anything else inside. The one thing that does work is the chime that comes on when your door is open and your keys in the ignition. That will work but only for a second or two, then u can close the door and it will do it again. When the door is closed and the key is in the on position the chime for that will also come on and does not shut off like the other. I have checked the starter conections, and all the grounds to the engine, and elect plugs. Do you think you can help? I would love not to have to take it to the shop as I have more in this repair than what I wanted anyways.