97modifiedmustangGT

When we boughtthe car the only rust on it was on the hatch so today we went to the junkyard to find a new one. We took the old one off and there were three wiring harnesses that needed to be unclipped in order to remove the old hatch. I hope some of you guys have some experience with what these harnesses are. What I think they are is just the defrost, licence plate lights and then the brake light on the wing. the new hatch only had one of the harness clips that worked with what we had. the brake light worked and we checked the headlights and they worked. We were lining everything up and then for some reason I went to pop open the gas door and nothing; so I think maybe the ignition has to be on and when I turned the key the fuel pump didn't even turn on. The car won't even crank and it is always making these random beeps. I seem to think we have shorted something out but don't even know where to look?? Any Ideas??

If it makes a difference the hatch is a off a 93 and we have an 87. They are both lx's. Was something different in these years???