Engine won't start

I failed to get the engine started today. Have a new alternator, starter and fuel pump installed on a 66 273 block just put into a 65 Dart. The horn, lights and signals all work but I have no Alternator (dummy light) when I turn the key to on. There is one wire in the wire harness that has a female spade connector bundled in the harness near the alternator. It is fairly long and I see no where it should connect. Is this the reason I can not start the engine? Is this something to do with the ignition? All other wires I managed to hook up by memory when I swapped the engine after the tranny was refreshed. Any help out there on my dilemma? I' m about 1 week away from abandoning the attempt to start till next year as it is getting to cold to work on the car at this point.